A good idea but the Pedia is, I think, a very bad place for this kind of info. Maybe some sort of 'show all/show this base' toggle under the General Stores menu?
OK, I decided for this option instead of global hotkey from geoscape.
Sorting by space used (by toggle button) has been replaced by sorting arrows (similar to load/save dialog), and you can now sort by all columns (name, quantity, size, space used) ascending and descending.
The toggle button has been renamed to "Grand Total", which displays "all items", including:
1. all items in stores from all bases
2a. all items in craft from all bases (both parked in hangar and out there flying around)
2b. all craft weapons and ammo
2c. all craft vehicles and ammo
3. all armor worn by soldiers
4. all items and aliens currently being researched/interrogated
5a. all items in transfer
5b. all craft equipment, craft weapons+ammo and craft vehicles+ammo in transfer
I hope I didn't forget anything
It will NOT show:
a/ soldiers
b/ engineers/scientists
c/ craft (names)
See attached screenshot.
EDIT: I didn't implement the "watchlist", because you can now sort by name and find your item relatively quickly... if you know what you're looking for