There's Repair Friendly Autofill for when using tools but when you want to repair them at an XP farm this feature can be a little tedious (especially if you need to use your sword to get the XP), unless you turn off Repair Friendly Autofill entirely while repairing, you end up limited to only repairing the remaining 9 slots in the hotbar and offhand at a time and you need to keep their higher durability counterparts out of the inventory all together, I know if you have AFKable XP you can also keep the inventory open so the Repair Friendly Autofill doesn't steal away the item(s) that need repair for their "safe to use" counterparts but this isn't always feasible. So I think an (optional) hotkey could be really useful for swapping instead to a "repair mode" would be really useful

I'd suggest that in "repair mode" if you have either nothing or a full durability+mending tool/armour piece/weapon in your off-hand it'll be swapped out for any mending item that has less than 100% durability and once everything is repaired the mode turns off automatically and a back up of also turning off when 30 seconds of no repairing has occurred (perhaps XP came from a limited source rather than a farm) and/or changing dimension and/or logging in such that Repair Friendly Autofill mode would be back on reliably and automatically as people might forget to hotkey back or get hotkeys mixed up and unintentional loss of item(s) can be avoided which I'm guessing is one of the points of the mod