[rafi1]

or you could, when you focus on/highlight an item a little popup appears with the relevant info on it

Exactly, you can see that in the second picture above, where the "added date" shows only when you select/over an item. The rest of the details are visiable in the right pane anyways.  I like to fill up the line with *actual* "media info" data as much as possible, and the view-name also suggests...

i sometimes put 2 $INFO labels in same tag and separate them using [CR] 
this will then show one label above the other(in same 'space' on the line)

Like what additional info? There is no sense to add info you already see on the right...
I wanted to add the file size, but this ".Size" property seems like a bug, and is not working for a long time in Kodi...