If I have to pick something, I'd say the thumb clusters. I barely use the top ones in the center because they're a bit of an awkward reach for my hand size. The bottom ones on the outside are also weird because you'd need to do some finger curl or move your hands. I just ended up mapping the keys I don't use as much over there and it hasn't been an issue, but it is some wasted potential :)

I use both but I'm terrible at taking meds regularly (ha, the irony!).
For losing track of time during meetings/focus sessions, I use a Time Timer to visually see time passing by/showing how much time is left.
For reminders, I use Due on iOS (+ Apple Watch) as it continues to send reminders until you do the thing and check it off.
For to-do lists, I use both paper planning with a bullet journal-esque notation as well as a whiteboard for "temporary" planning, like creating a prioritization matrix, as it allows me to shift things around more easily.

Missing the keyboard smash and the xyz_final_final