I just want to share a nice solution so everyone can still work with documentsset combine with PowerApps.
Here is my solution what works great
Make an PowerApps forms, inside the form you can combine all the logics what you need. For example, i made 4 casciding fields. At the end of my form i made a button, New Documents set. This button saves the data info a lists and open a new Documentset. This is also the trigger for my Flow. The flow send the information from the this into my new documentset. After the documentsset is updated, the flow will delete the item from the PowerApps forms.
After the documentset is made, a new flow send the documentset to the correct library. With PowerApps, Flow an SPO we made a nice solution to use documentset.
If anyone has an question, i would love you to help you!