As you see above we don't see the "Faction permission" block in inventory, same in the hotbar. Impossible to distinguish an empty slot and a slot fill with the block. It's quite annoying and can be tricky if the hotbar is empty or if we are looking for it in the inventory using the filter (user assume getting an empty result).
Same for the Area trigger block which don't have icon too.
I was on single player creative mode, I didn't try to switch in crafting mode to see nor multi.