It’s hard to tell whether presets accumulate or when I pick a different one the one before it is overridden. On the one hand, the UI implies that each choice overrides the one before. But when I do undo it names each sequential preset command, making me think they might be accumulating.
Also “most recent edit” is not clear. What edit is that referring to?
The interface has a checkbox at the bottom of the preset UI: “Replace Edits with Preset”.
If that is checked, then presets will replace all current edits on the image. If it is not checked, then it will apply the preset on top of the edits. Undo and Redo work to restore the state before and after the preset was applied.
With the checkbox off, as if I did the edits by hand one after the other and just accumulate.
With it on, it is as if I started with the unedited image and applied the preset. So not only does the reset replace other presets that were previously applied, it replaces all edits to the image up to that point.