Some symptoms only happen during certain activities, like “motion sickness” which may only happen when on transportation, for example. Or some that are not always tracked, like “high resting heart rate” on days you don’t wear a pulse monitor of any sort. I would like to be able to track symptoms only on the days they are actually possible, and not have every day included in the statistics for that symptom, only the ones where it is applicable! That way, I could see what days I actually had zero motion sickness during travel, and see what other factors might impact the likelihood of motion sickness (for example) on days that I travel, without those “none” statistics being hidden within or skewed by days where the symptom couldn’t happen.