I have a note’s tab pinned. When I click the same note in the file explorer a new tab is created for the same note.
The expected behavior would be to switch the focus to the pinned one. Indeed, I feel this should be the case for any note/tab, but, at least, should honor the pinned status.
In the meantime, you can try to find a community plugin to help. “No Dupe Leaves” is one, and I think another exists too. Although I remember trying it, and there were some circumstances where it would still open a duplicate. Not all commands were covered.