I posted this in the official Discord, but so it won't get lost in the chat I'm also going to be posting this here.

I'd personally love a toggle added to the countdown so that after the countdown ends it begins counting up. Useful for when taking a break and you go a bit over so people can see you've gone over and for how long.

You could also let people select a general timer as well counting up. So after selecting the countdown layer to your scene you could choose to leave it as a basic countdown, change it to a countdown that transitions to counting up when the timer expires (and perhaps even have the color of the text change at this point as well), or change it to a basic timer counting up.