Thank you for your patience. Please find our answer below. It’s a short summary after longer investigation and conversations with the team.

Tab Islands / Tab groups
We decided TI, in its current shape, doesn't fit AIR’s vision and is not aligned with UI. Therefore, it remains disabled to avoid unexpected experiences. We plan to adjust it in future and enable it in AIR, but currently it’s not our priority.
While doing the investigation for you, we were also searching for a solid workaround within the code but didn’t find anything of enough quality.

Extensions from chrome: store
Opera is not Chrome and vice versa. They're specific features that are not available in other browsers. There is a reason for it, and it impacts many things. That’s we have a dedicated store for extensions, which is maintained by a dedicated team. It’s still possible to install many of the chrome extensions outside the store, but we can’t guarantee their functionality.

Vertical tabs
This is an old topic among Opera users, but the answer remains the same. There are currently no plans of supporting such functionality in any Opera.
The vertical tab extension you mentioned from Addons.opera.com is something made by an external user. It’s not our implementation, but was reviewed and accepted by us.

Many thanks for all the in-depth questions, you seem to be a truly engaged Opera user. (edited)

Don't worry, we still remember about you. Expect answers soon.

i feel you. in my case i just switched to normal opera, got rid of everything in the app thing sidebar except aria , decluttered the awful speed dial and went on to enjoy a little, i get you, this is beautiful but awful to use , im really hoping opera actually improves on this, then i might finally switch

man I'm glad I'm not alone.
but it's been 2 month!
and @Mlipka hasn't replied
or anyone else from the team
for that matter

I'm afraid they'll ditch this cool browser to work on
Opera Neon!

@salimalbitar Wow! Thanks for all the details and such diligent investigation.
I'll pass it to the team and investigate deeper. This might take some time, I will return once know more.

yeah, I did everything I can do from my part lol

and I'll be patiently wait for your reply ️

I received a "race condition" error which prevented tab from opening next to the current one

i tried to find any wiggle room, but I couldn't

• I've already tried introducing a delay (setTimeout).
• I've tried explicitly activating the tab (active: true).
• There's no "force move" flag in the chrome.tabs.move API.
• I cannot inject code directly into Opera's core browser process to disable its native tab placement.

as for the tab duplication extension:

there's a tab duplication extension in the store, but it doesn't have any shortcut keys
(like other chromium extensions on the chrome store)

but just to be sure, here are the extensions I've tried
(and didn't work):

1. always right:
   https://github.com/autonome/always-right

2. duplicate-tab:
   https://github.com/zertosh/duplicate-tab

3. duplicate-tab:
   https://github.com/stefansundin/duplicate-tab

4. open-tabs-next-to-current
   https://github.com/sblask/webextension-open-tabs-next-to-current

alongside the extensions I created myself:
https://drive.google.com/drive/folders/1Lz_L_Gmu2WGtRRrh2myVQhE-c_6C0p_I?usp=sharing

I tried all the tabs above in other chromium based browsers, and they're working fine

thank you again for the follow up and the work
now and later on

and once Opera is ready to be used again
(tab islands introduced and/or chromium extension are supported)
I'll happily make the switch.

P.S.
try taking a few notes from sidekick browser
(the adding tasks for example seems like a good idea to implement)

Hi @salimalbitar

Thanks for taking the time and sharing your thoughts. We appreciate the feedback. We'll analyze it.

In the meantime, can you share exactly which extensions work for Chrome but doesn't work for Opera? This way, we can investigate the root of the problem.

Both browsers use chromium as their engine, and extensions from Google store should work exactly the same in both browsers.

Hey @Mlipka
thank you for your reply it shows that you guys care ️
this makes sure Opera Air doesn't suffer the same fate as Opera's crypto browser lol

Can we assume that
most chrome extensions don't work on Opera?
because it seems like Opera Air is
restricting certain (most) Chromium APIs!

at 1st I thought
it just does not support the chrome.tabs.group API
because it may conflict with the tab island feature (that's not even introduced to Opera Air yet)
(which doesn't make much sense, but ok..)

but then I found out that the same problem is happening with other extensions as well

here's why I think that Opera Air is restricting Chromium APIs:

since "Tab islands" are supported.. yet.
(please add the feature to Opera Air soon)
I was like it's ok.. I'll just use a tab grouping extension from the store
but after all the tab grouping didn't work,
I created my own extension to see what's wrong

then I got this error

Error creating group: Grouping is not supported by tabs in this window.
Context
background.js
Stack Trace
background.js:43 (anonymous function)
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// Listen for when the extension icon is clicked
chrome.action.onClicked.addListener((tab) => {
// Get the current window's tabs
chrome.tabs.query({ currentWindow: true }, (allTabs) => {
if (chrome.runtime.lastError) {
console.error("Error querying all tabs:", chrome.runtime.lastError.message);
return;
}

// Find the active tab in the current window
const activeTab = allTabs.find(t => t.id === tab.id);

if (!activeTab) {
  console.error("Active tab not found.");
  return;
}

// Filter tabs that are to the right of the active tab
const tabsToGroupIds = allTabs
  .filter(t => t.index > activeTab.index)
  .map(t => t.id);

if (tabsToGroupIds.length === 0) {
  // Notify the user that there are no tabs to group
  console.log("No tabs to the right to group.");
  chrome.notifications.create({
    type: 'basic',
    // iconUrl: 'icons/icon48.png', // Removed as icons are not provided
    title: 'Tab Grouper',
    message: 'No tabs to the right of the current tab to group.',
    priority: 0
  });
  return;
}

// Get the current group counter from storage
chrome.storage.local.get({ groupCounter: 0 }, (data) => {
  let groupCounter = data.groupCounter + 1;

  // Create a new tab group with these tabs
  chrome.tabs.group({ tabIds: tabsToGroupIds }, (groupId) => {
    if (chrome.runtime.lastError) {
      console.error("Error creating group:", chrome.runtime.lastError.message);
      return;
    }

I was chatting with Manus AI about the tab grouping error I got and it told me that:

"This error message:
"Error creating group: Grouping is not supported by tabs in this window."
is very specific and tells us exactly what the problem is.
It means that the browser you are using (Opera Air, in this case) is explicitly reporting that it does not support the chrome.tabs.group API for extensions in the current window.
While Opera browsers are built on Chromium (the same base as Chrome), they may choose to implement or restrict certain Chromium APIs.

Opera's "Tab Islands" is a native, core feature of their browser, and it's highly likely that they have disabled or not implemented the standard Chrome Tab Grouping API for extensions to prevent conflicts or to maintain control over their own tab management system.

What this error means for your extension:

• The code itself is likely correct for a standard Chrome browser.
  *The limitation is with Opera Air.

The browser environment you're running the extension in is telling you that
it doesn't allow extensions to create tab groups using this method."

and since I tried the extension on chrome:
this confirms that:

The limitation is specifically with Opera Air's implementation of these APIs

Thanks for taking the time and sharing your thoughts. We appreciate the feedback. We'll analyze it.

In the meantime, can you share exactly which extensions work for Chrome but doesn't work for Opera? This way, we can investigate the root of the problem.

Both browsers use chromium as their engine, and extensions from Google store should work exactly the same in both browsers.