I decided I wanted to play as a dryad, so I copied the stats over to a homebrew race. The Dryad is able to cast Shilleagh once per dawn, so I added that along with the other spells Dryad has. 

Because Shilleagh is a cantrip, limiting it to one use a dawn breaks the character sheet. Once you click cast, it uses up the one charge, but because it is a cantrip, the sheet assumes it has infinite uses, and thus doesn't provide a box to click to recharge it. The "Cast" button goes gray as intended, but there is no way to recharge that one use.

It could be fixed by making the homebrew daily restriction override the sheet so that the "uses left" box is shown instead of it just saying "cantrip".

Alternatively, a "Dawn" button could be added next to the long and short-rest buttons for character's dawn-based abilities to reset.

Oops I forgot the link to where I found the bug: https://www.dndbeyond.com/profile/Great_AxeAlt/characters/49365330

The limitation for the Dryad states “1/day,” not “1/dawn.” A “day” is dawn-dawn for magic items, but for creatures (especially PCs) it means Long Rest-Long Rest. Simply alter the “reset type” to read “long rest,” that should do you.

In a somewhat similar predicament, I wound up making a homebrew copy of Shillelagh changed to a 1st-level spell without upcasting so I could attach it to a feat for 1 use/day and have the checkbox show up. Just so that you have a way of dealing with the issue now.

Edit: Oh. Use Sposta's way, it's simpler than mine. (My version still made sense to use with a Dawn recharge since it was a feat for providing 1/dawn uses of spells for an Instrument of the Bards.)

Quote from IamSposta >>

The limitation for the Dryad states “1/day,” not “1/dawn.” A “day” is dawn-dawn for magic items, but for creatures (especially PCs) it means Long Rest-Long Rest. Simply alter the “reset type” to read “long rest,” that should do you.

 I never knew about the dfference in "day" definition for items and creatures, thanks!