This feat represents the number of spell slots given to a warlock 3rd caster, such as a Profane Soul Blood Hunter, an Eldritch Marauder Rogue, or a Way of the Dark Disciple Monk. It's not too hard to track, but given that Profane Soul's spell slots don't work well all the time in the sheet, and there's no way to program warlock 3rd caster spell slots as homebrew (thank you DnDBeyond for keeping the homebrew creator updated all the time with brand new features every month as it totally has changed in the past 2 years, believe me), may as well find a way to integrate the tracking into a character sheet, and this is it.

To cast one of your warlock spells of 1st level or higher, you must expend a spell slot. You regain all expended spell slots when you finish a short or long rest. For example, when you are 15th level, you have two 3rd-level spell slots. To cast the 1st-level spell hex, you must spend one of those slots, and you cast it as a 3rd-level spell.