Yes, it would be great if labels could refer also to Drawings. Or at least if Drawing's Title was accessible outside of Layouts.
At the end I figured out some kind of workaround. I copied my Drawing to a Layout, turned on the Title and then copied it again and pasted it back on a Worksheet.
That way, the Drawing kept its Title, even though it is still greyed out when i open the settings.
So now, when I want to link in a new DWG, I just copy an old Drawing with Title, relink its contents and it updates also the Title automatically.