My DM has given me a unique boon as a Warlock/Bard hybrid. I've been permanently imbued with the following abilities:

• I can cast Sending at will, without using spell slots.
• I can cast my choice of Command or Suggestion up to 3 times a Long Rest, without consuming spell slots; however, both of these castings share the same pool of charges and still use my spell save DC.

I'm trying to figure out how to add these to my sheet via the Homebrew editor.

If I make it a feat, then casting Sending "at will" is easy to add to it, as is adding 1 spell that has charges. The trouble is then adding the ability to cast two different spells that share the same charge pool; if I put the two spells together on the feat then it just gives me a dropdown on the character sheet and forces me to choose between them, rather than letting me attach the charges to both. Is what I'm after even possible in D&D Beyond, or am I just missing something?

What you seek to do is not possible with Feats.

The closest is adding the spells at will (or not add them if too confusing) and making a single action that describes being able to cast one of the spells. You can give that action 2 limited uses. However, if you add the spells at-will they will show as this in Spells tab and can be confusing. If you don't add the spells they won't show up in the spells tab - the closest is a tooltip in the action. This can make it awkward to look up the spells.

Alternatively, make a Magic Item with 3 charges and add the spells each with min and max charges set to 1. Then they'll have the same charges pool. A feat can be used for the main feature text and adding the at-will spell and the item is just a way to have the effect on your sheet.