When browsing the library while listening to music, there are album artworks all other the place, as seen in the screenshots.
This is why I think it would be more logical to just right-click on the artwork one wishes to enlarge.
Also, it has already been implemented this way for the Album and Tracks view.
I think adding an additional entry in the context menus would be the simplest way to implement it and the simplest to discover as a user.
Thanks for your suggestion, it would be a bit quicker, but one would have to remember the shortcut (and I am not very good at this).