Could there be some user defined data types somehow? For instance:
Day of week
At work / at home etc.
Perceived mood / mental state
The user would create a new data type, name it, and then define possible values. Then they fill it in like a diary: “at work / off work” or “calm / stressed / happy / anxious”. Maybe they give something a score on a scale out of ten. This is then included in the analysis like all the other data types.
For this one you can do this now with the Health app’s State of Mind recording. That shows up in This & That as “Momentary Emotion” and “Daily Mood”, depending on whether you recorded it as “how you feel right now” or “how you’ve felt overall today”.
I tend to pick one or the other and only use that, because I’m too lazy to log it more than once a day. But if I were being more diligent about it, having both would be great I think.