So, in a workflow where you do multiple things. Like first applying a standard stack of photo adjustments to get the photo right, and then maybe going further to work with other presets like Simplify/Impression/... Maybe just experiment a little.
Currently, the only option to proceed with such combos is to Duplicate/Apply, and then proceed checking out the next steps in presets. Because any clicking on a preset will otherwise reset the current adjustment stack and any previous work you have done.
This leads to multiple issues.
a) you might end up with 10-15 intermediary and unnecessary "photos" in the film-strip. To figure out what preceded your current step, you have to go back to earlier and unnecessary versions.
b) It is completely impossible to remember what all the changes were, since all these intermediary steps and "Applications" hide the combined set of adjustments that created the overall effect. (As witnessed by all the times users are asked "How did you do this?", and the answer is "I do not know."
So.. Hence my suggestion.. The ability to group adjustments (for easier overview) but more importantly, a way to "LOCK" existing adjustments/layers in place, so they stay in place, even if a new preset (one of more being tested) is clicked. Without having to do all the "Duplicate/Apply"s along the way, cluttering up the workflow and confusing the process.
This will also allow a combined "preset" to be saved, that documents the whole process. From beginning to end.
Note that this is also somewhat related to this RFC: