Opera Version:56.0.3051.43
I haven't seen such notification windows with any other browser.
Some weeks ago there started to appear small notification windows in right bottom corner - mostly kind of adds.
My first reaction was malware or virus but this doesn't appear to be the problem.
When clicking in this small windows settings icon - it opens Opera settings, block adds in upper position.
I have switched blocking on, cleared exceptions but these notifications still continue to appear.

Any idea how to stop this Opera behavior?

@burnout426

Thanks to all. i believe this not so easy to find list fixed my problem.

Things have got worse after GDPR.
When working hard searching solution for some technical problem with Google, it doesn't feel like being eager to read all of these tens of pop up windows asking to accept GDPR, cookies or something else, like notifications now.

Just an hour ago my Opera browser lost capability to save web pages as mhtml.
Is there any chances to restore this functionality?

From web I found several similar topics but not any understandable explanation what happened. and how to fix.

@leocg
Not much of help to know the name of evil.
But who is Chromium and why it changes my Opera settings?
How to restore Opera normal behavior to save mhtml?

Why can't it be enabled by typing "opera://flags#save-page-as-mhtml" at the address bar?

Thanks.

@burnout426 said in How to prohibit opening 2nd Opera window:

I can't reproduce this. Sounds like your control key is failing to activate sometimes when clicking as if you were holding down just shift.

Do you hold down ctrl, hold down shift and then click or do you try to hit ctrl + shift and click all at the same time? If the latter, the chances of it not working correctly are higher.

I am afraid you hit the nail head - my keyboard ctrl is a little bit tired and kbd probably needs replacement.
There have been also occasions when ctrl+c didn't work.
I just didn't know there might be another shortcut so similar.
I try to keep in mind to provide later feedback. (but as well if there isn't any reply in 2 weeks this was a solution)

My posting was initiated because this flaw also deleted all previously opened tabs history.
Reopening Opera didn't include previously opened tabs.

Usually I use ctrl+shift when clicking to link for opening in tab but sometimes Opera opens new window.
How to avoid this and limit Opera only to new tabs?

With 2nd Opera instance is a problem, that when forgot and going to close Opera, then Opera may not restore main content but only this last single link.

@leocg
Thanks, I try to gather some statistics, when it happens.
But IMO it's often Ebay which may start new Opera but it's not a rule.
If not closed instantly consequences are fatal.
All history is gone. (replaced with this single Opera window without any history.)

@leocg

Yes new sessions and tabs files are always created.

@leocg

Tabs with same url and name aren't equal, which makes search not very effective.
Often there is advanced search strings included, which is important to restore.
Some pages found earlier I don't remember name.
But I keep trying.

Bad surprise is that some tabs I recovered today, were lost again after renaming sessions folder and then restoring folder name.
Looks like Sessions folder session and Tabs file are not linked directly.

@oberator
PS. A follow up to my previous posting.
Looks like Sessions and tabs files in same folder are not directly linked with each other.
I saved old folder and started using Opera with several tabs opened.
Closing and reopening Opera restored today's tabs as expected.
For testing purposes I renamed sessions folder to sessions2 and copied old 06.08.21 content into sessions folder. When results were not what expected, I deleted sessions folder and renamed sessions2 folder back to sessions.
When reopening folder all today created/recovered tabs were again missing.

@leocg
I think I tried all combinations.
Below is the list of files and tried use name of new session 07.08.2021 09:50 Session_13272742572809744 to Tabs file and session name.

Those with date 06.08.2021 are expected to be correct, Tabs files looking with notepad contain familiar URL's ...
Looks like this 06.08.2021 19:55 sessions file isn't linked to any tabs file.

06.08.2021 19:55 1,303 Session_13272742551560493
07.08.2021 09:50 1,406 Session_13272742572809744
06.08.2021 19:55 212,680 Tabs_13272742551362498
06.08.2021 19:56 212,680 Tabs_13272742572593433

05.10.2019 10:37 4,973 session_8ceb3838-2774-4cad-9809-00a5c09c01d2.raw~RF184ff91c.TMP

After loss off current session open URL's and special web page related operators, all I have left seems to be browsing history to restore previously open tabs.

Since history has hundreds of repetitive entries, it's quite time consuming work.
Is there any tools to manage and sort history, browse it directly without opening each url one by one?
And to save it for later work?

Thanks

@leocg
There are 2 tabs file of same size 208 Kb but no old session file.
Combining Tab file with new doesn't work, since Opera "last" is always restored from session file.
With notepad I see that Tab file content is what needs to be restored.

@leocg
I found Windows 7 :\Users\user\AppData\Roaming\Opera Software\Opera Stable\Sessions file name Tabs_13272742551362498 but is it possible to load with Opera browser?

How to restore Opera last open url list?

Opera just swiped off all my previously open web pages and now there remained a new single
start page only.

Might there be any previously opened url configuration file for restoration?
Some open URL's were not so easy to find.

@burnout426 said in How to prohibit opening 2nd Opera window:

I can't reproduce this. Sounds like your control key is failing to activate sometimes when clicking as if you were holding down just shift.

Do you hold down ctrl, hold down shift and then click or do you try to hit ctrl + shift and click all at the same time? If the latter, the chances of it not working correctly are higher.

I am afraid you hit the nail head - my keyboard ctrl is a little bit tired and kbd probably needs replacement.
There have been also occasions when ctrl+c didn't work.
I just didn't know there might be another shortcut so similar.
I try to keep in mind to provide later feedback. (but as well if there isn't any reply in 2 weeks this was a solution)

My posting was initiated because this flaw also deleted all previously opened tabs history.
Reopening Opera didn't include previously opened tabs.

Correct is obviously that Opera opens new Window when not expected.
Today I have tested Ebay ctrl+shift opens new window instead new tab approximately 1 of 5.
Repetitive opening same link new window instead new tab is same approximately 1 of 5.

When main Opera Window is closed 1st and any extra Opera window closed 2nd, then restarting Opera doesn't restore main window but this extra without any history records.

Rather tedious to keep track of this behavior.