I am currently creating a magic item which has a set amount of charges and can use 1 charge to cast one of the available spells. For some reason, I cannot find a way for the [1 c] button to appear next to any cantrip level spells, so that it will auto-spend the charge. The item allows the cantrip level spells to be cast at will, which I do not want. Is there a way to do what I want currently in the Homebrew Content Creator?

Cantrips appear to be locked in as "at will" when an item gives them to a caster. BUT... you can do what you want by creating a homebrew copy of the cantrip. Just homebrew a spell, use the cantrip you want as a template, then change it from a cantrip to a 1st level spell. Leave everything else the same, but change the name to something different. Then, add that homebrew spell to the item. It will appear as a 1st level spell instead of a cantrip, but it will have the 1c button and use charges.

Thank you for the convenient work around!

This Bug has still not been addressed and was first mentioned 3 years ago?

While the work around does function it requires a lot more work than simply selecting the spell.