1,2,3.4, LMB, RMB, Q should be slots - what they display will change.
I wouldn’t bother with slots for the 6 small elements on the right - they’re always the same. And if you only want to left click them, I’d even risk using buttons here (still wrapped in a user widget because I may want to update them later).
But they can still be slots, it makes it easier if there’s more than 1 person working on the project. You prepare slots for the layout and a more artistic team member can drop a pretty widget there.
And if you decide to move that slot elsewhere, everything will still work.
Inventories are complex. I’ve made a few and it generally does not get easy.