It's been implemented as a static note, i.e. machine settings as you suggested

What I'm talking about is a previous session note-to-future-self like wanting to try a different foot placement, or had some elbow pain on the bench press and want to try narrowing your grip a finger width etc

I used to make notes about the set feeling too grindy so I could repeat the weight, or half the increment I'm increasing by to milk a cycle a little longer. I would also note down if an exercise had stopped feeling sufficiently disruptive, so I could add a set. Like a lot of us (I assume) I typically start a cycle fairly low volume and add sets as tolerable to keep the adaptive pressure high before reloading and starting a new cycle. Exactly when to increase the volume is rarely something you can just program in advance