How to log non FB workouts?

Hi there, I've been sedentary the last few months and finally starting to feel like it's time to get back on the wagon and do another FB program. I want to do it at my own pace and I know how to adjust the calendar for if I take extra rest days etc.

I'm wondering if anyone has a good idea for days where I do other activities? If I push off my FB workout in favor of another activity like swimming or skating or hiking, what's a good way to put it in my calendar? Is there a way? Or should I just add any video on there just so I can mark it complete. I just want a way to show it wasn't a rest day, those green check marks are so motivating.

Thanks! Can't wait to get back on the wagon.