I've been using Kate under Ubuntu for several years now. When I single-click on a folder or file in the left pane, it opens.

On my new Mint machine Kate (and several other apps) take two clicks to open folders and files. Not worried about most of them but I use Kate quite a bit and it gets annoying. This is not (apparently) related to caja, which obeys the single-click mode I set but it does relate to the file-selector popups for most (probably all) apps.

I SUSPECT the fault lies with KDE but can't find a remedy for either Kate or KDE.

In the Control Centre there is an option to launch KDE System Settings (also in the Preferences menu but it fails to launch from there). Selecting Default Applications leads to a File Manager setup tab. There is an option to select a Default Component (VLC or Other) but the text on the top of the panel suggests there should be other settings to setup the file manager itself. I THINK, if this were available, it might allow me to select Single Click.

Or is there another way I've missed?

Also - is there a way to view hidden files/folders in the app file selectors? That is particularly annoying when setting up a variety of config files for the first time.