Is there a way to forbid from launching multiple copies of DO?

[Cracknut]

Can't find anything in settings

[Leo]

There is never more than one dopus.exe process running at once, but if you want to restrict things to a single window then see here:

Always re-use a single window instead of opening new windows

( See Also: Middle click folder to open in new folder tab ) If you only ever want to have a single Opus window open then the following options will help. Note that the first two screenshots are not the same, one is for Desktop Double-click and the …

[Cracknut]

It works only in part. For example, if I open file explorer from another program, for example visual studio - right click on project - open folder in file explorer, it still opens a new DO lister. This can't be changed?

[Leo]

Preferences / Launching Opus / Explorer Replacement / Open external folders in a new tab from the linked guide covers that.