How do I make 2 different commands go towards one counter?

Hiya, this is not possible.

I ran into a similar challenge in trying to transition from Streamelements to Nighbot, missing the ability to dynamically modify a counter or just get the current count without changing the number.

I believe you could utilize an external API to achieve the result (such as twitch.center). You can set a "quote" with your counter and then use the various commands to selectively modify that same counter.