Currently you can view backpack with [I] command. Manipulate item submenu was a big step forward in UI since it allows to use item right away without quitting backpack menu, looking for correct key and looking for and item again.

However it lack the most common use case - equipping. So you have to follow and old scheme - navigate to inventory screen, look for the correct slot, unequip item if any and look for item which you wanted to equip once again.

Suggestion is simple - add "equip" command to "manipulate item" menu. My preference would be to unequip items automatically if slot is occupied but I'm not insisting on it.

Some thought on edge cases...

• Equipping ring should give an error if gauntlets are equipped. Although I'd prefer a warning with a prompt asking whether I want to remove the gauntlets to equip this ring.
• If slot is blocked by cursed item an error should be given. E.g. you won't be able to equip armor if you're already wearing one and wearing cursed girdle.
• If you're trying to equip an item which fits more than one slot either additional prompt or multiple "equip with" commands should be there. E.g. torch can be equipped with right hand, with left hand and in tool slot.
• I rarely want to equip, say, clothes in missile slot or with my hand but I don't mind if such possibility will be in manipulate item menu as well.