Arcisun

Yes, that's the button we are referring to. When you click those buttons currently, they apply a destructive edit directly to the currently active layer. It would be perfect if they instead created a new Levels Adjustment layer with the changes. This would be non-destructive, and a good starting point for further manual adjustments, as OP suggested. OP's suggestion of adding an Auto button to Affinity's current Levels Adjustment Layer, would also be really nice. Photoshop Elements 14 had this, and it was amazing for a good starting point to work with. Here's what it looks like in Elements 14 for reference:

I just finished my free trial, and this suggestion is one thing holding me back from purchasing (very on the fence right now). The cheap old copy of Photoshop Elements 14 I picked up years ago has an Auto Levels button in its level adjustment layer. I used that feature a lot. I'd love to see it added to Affinity Photo. The second suggestion by OP is also really smart. Would love to see that change as well.