Whenever you source a file on the terminal, it only applies to the terminal session. No matter what file it is.

Sounds like a good deal.

The same behavior happens for me in a different file browser (Nemo) and a different Desktop (Cinnamon). So I’m pretty confident, it is no isolated KDE issue.

That is definitely an annoyance. But the cause is not your file browser or KDE. The webdav has been mounted to the system and when an application tries to use it, it runs into a timeout. You can’t even unmount it, since that requires the system to talk to the network drive.

This is also not limited to webdav, it happens with all kinds of network drives. This is something that needs to be addressed at the core level of Linux. But I have no expertise, so no real clue where exactly.