Closing the window during an update is supported, you don’t have to worry about it. Discover continues running in the background, and shows a notification until the update is complete.

It is editable by default… Once you click on it, it turns into a normal text field

That really sucks. Sadly, when I looked into this a while ago because it happened on my PC, noone knew why it was happening :(

One potential workaround could be to use krunner for starting apps instead. I think it doesn’t happen there