The relevant actual versions I have:
Firefox is 73.0.1
KeePass is 2.44
KeePassRPC is 1.10.0.0
There are no such effects in this environment.
It doesn’t matter what browser I use (Chrome, Chrome based Edge or Firefox)
I found the reason. When you choose “always on top” in Keepass the kee dialogs when choosing to edit the form fields they hide in the taskbar and it’s impossible to view them except when doing alt+tab and even then it’s not possible to view them.