Is there a way to copy the all stages from one match to another?

There is a better way maintaining stage library in the PractiScore app for Android.

You can build a “library” of your standard stages and avoid cloned matches disconnected from the match registrations.

Go to the match list. Select a match you want to reuse stages from and from the match menu on the right select “Library”. It will show a “Library” marker on the match.

Then after importing your match registration using pin# go to the stages and use “Add Classifier” option to add your stages from the library.

PS: in the PractiScore 2 app the Library flag can be set on the match editing screen.