That could work.
With both next to each other I find the larger icons a bit clunky. The smaller ones came about due to the way I was snapping to pixel dimensions. They're still clear even at such a small scale, but I can change it if people want it.
True. The new design was based on @stealthstylel's suggestion (with the orientation rotated to represent the button "filling up" with compounds. The checkpoints could still be added as markers on the button but I think that would be a little cluttered. Perhaps a bar is the best option after all.
For the NPC microbes, it is save. For your own, it overwrites the species details but unlike save doesn't record the compound levels or other attributes of your individual at that moment.
Derp. Good spot. I mainly put a title there because there was a lot of free space at the top of the panel which couldn't be filled by another bar (since it's thinner than the rest). It could be removed really.
It's supposed to be going up, as if liquid is filling it. Disabled buttons will be dark, so the logic was that the editor button would progress from grey to blue as it gradually approached availability.