In comment https://github.com/geany/geany/issues/3961#issuecomment-2373617833 you wrote:
Up to you to raise a separate feature request to change the behaviour and see what others think (of course an attached PR will usually be considered positively ;-)
Why should I request a separate feature request if everything necessary is said in this issue. As I mentioned in my last comment, if you reopen the issue and remove the label, I will change the title of the issue. The title will then be `A release of a click on a tab-title of the sidebar should put always the content-area of the tab in focus` instead of `BUG: A release of a click on a tab-title of the sidebar does not put always the content-area of the tab in focus`. Because I'm not a software developer but a software user, I can't offer a PR.
Regardless of this feature request I have the intention to contact GTK to ask if they can change the GTK default behavior.