I double-checked: If I let the URL dropdown fold "up" by clicking somewhere else, then switch the tab forth and back, its content still disappears. If I instead switch to a different application on my PC, the content stays.

This is on Linux:
Opera One(version: 136.0.5995.0)
Update stream:developer
System:Fedora Linux 44 (Workstation Edition) (x86_64; GNOME)

I noticed another very annoying thing, which makes Operas less easy to use:
The URL bar loses my typed content, if I switch to a different tab, or a different window (via window manager).

Like e.g. I open a new tab, or switch to the URL bar with Ctrl+L, so to enter a new search term for my default search engine or any other string (even a URL), then switch to a different tab to look something up, or if I let Opera lose focus while I do something else on my PC, in a different program. Whatever I have typed just disappears when I return to my tab! Totally impractical.

BTW: What used to also happen was when switching back and forth between tabs, if one tab had its focus IN the URL bar, when returning to that tab, the focus was no longer there (but the text still was present). I had reported that MANY years ago and it was quickly fixed, but some time ago this "issue" returned and I wasn't sure whether that was intentional, so i stopped caring.

when i comes to opening a bookmark or history link, this did not change they just open after your current active tab as they always did

RNA-4324 [Search Engines] Opera triggers inactive search shortcuts in address bar

that was first included in the previous Opera Developer build as shown at https://blogs.opera.com/desktop/changelog-for-136/.

I mentioned this new issue in that bug at least, so someone is at least informed about it.

*It's unclear why the flag not only changes the new tab button position but also changes the way tabs are open.

Only recently did I notice that the search engine shortcuts have - partly - stopped working. My custom ones appear disabled, but I could (seemingly) reenable them manually.

But the "built-in" shortcuts - such as "w" for Wikipedia (the German version in my case, due to some mechanism inside Opera) - have also partly ceased to work. Typing "w Opera" into the URL field show bring me directly to Wikipedia, but directs my to the default search engine Google, using "https://www.google.com/search?client=opera&q=w [---]".

I have seen some changelog entries regarding "search", but I cannot usually understand what was changed from their cryptic titles. And I couldn't find anything in these forums.

Opera One(version: 136.0.5995.0)
Update stream:developer
System:Fedora Linux 44 (Workstation Edition) (x86_64; GNOME)

I have been observing this for a few versions now, on two different Linux machines with independent, different search engine configurations.

Has anyone else been seeing this?

RNA-4384 Remove separator above ‘Wallpapers’ title in easy setup

return the wallpapers toggle in EasySetup menu.

RNA-2097 Option ‘Force dark mode on pages’ resets after changing theme or mode

the toggle still works incorrectly (the synchronization EasySetup vs Settingss broken)

Improved visibility of the currently active tab in Vertical Tabs

• Again the new design for the island body in vertical tabs...
  You really think that the count of tabs in island is more important than name and highlighted body of island? Now the island's body looks like tab but the number of tabs is highlighted. The previous design (the solid background box for the island name) was better. The even more earlier design (the bright box + clear text) was even more better.

Now if speaking about bugs...

1. The island created while being in vertical mode will have no corresponding context menu.
   

2. In horizontal mode the new tab button and some last tabs will be hidden after expanding islands. After moving the cursor away from the tabstrip the elements will restore.