I confirmed the issue. It seems to happen sometimes when one opens or closes the IDE/sidebar very fast one after another. But as you said, it does not influence the functions.
This does usually not happen for me (but a few times I saw it). In my test, it usually simply brings the already open IDE window to the front, as in this video of a test:
I tried again and it happens for all the time. I don’t know where your open IDE window goes if you reopen kantu in a side bar. But mine stays all the time. That is why it opens multiple windows.
As you can see form the previous screen shot I’m at the same version you are.