Hi Baukje! Long time no see here 
For the inherit alpha part - DeifLou is working on it.
To summarize those 300 posts on this topic: Potential improvements to Inherit Alpha in Krita
There will be a new inheritance mode in krita for inheriting from a single layer below (like PS clipping mask).
It will be used when opening a PSD and you will be able to use these to save a valid PSD. Current inheritance will still be available, but if you plan to export to PSD - those will not be supported as Photoshop don’t have a feature like this.