Take a look at the Orb of the Stein Rune in the SKT file. It does exactly what you want.
- You want the field "trkMax" to be 1 (as in, one use per whatever, see next bullet).
- Add the tag group "Usage" with the tag "ShortRest". The ShortRest tag automatically resets on both a short and/or long rest, which is convenient.
- Add the tag group "Helper" with the tag "ItemSpell". This tells HL it's a spell coming from an item.
Your conditional I'm blanking on. Try it and see if it works.