I would love to have the option to put my most-damaged tool in a row D slot so that it gets used up and breaks before it's replaced with a new one, please. By sub-sort, I mean after items which match the rule in InvTweaksRules.txt have been found, only those items would be sorted.

Say I have a wooden pickaxe with 20 damage. I've just mined my first stone and crafted a stone pickaxe. The rule:
D1-A1 pickaxe
currently seems to favour putting the undamaged pickaxe in the D1 slot. I suggest the rule:
D1-A1d pickaxe
could be used to favour the pickaxe with higher damage value, regardless of its item ID.

The default order (which determines damage order for specifications that don't include a damage or allow any damage) is global so it can't be changed for specific slots.

It would be potentially possible to invert damage ordering on all tools however.

That would definitely do the trick. If you'd be willing to please put that option in, it would be very much appreciated, at least by me!