You can have as many “home automation” activities running at one time as you want.
You are limited to one “home entertainment” Activity at a time.
Unfortunately, IR controlled devices are considered entertainment devices.
Lots of people have requested a way around this, harmony always says they’ll think about it, meanwhile there is an official work around. It’s sort of a pain to set up, but it does work.
https://community.logitech.com/s/question/0D55A0000788jaUSAQ/creating-a-home-activity