Thanks Ralph and George for helpful suggestions!
At first I need to ask Software AG for a license key to unlock old editors.
Meanwhile I foound an article by Karlheinz Kronauer „Get ready for Natural 9” at Techcommunity. I’m worried about the following concerned with source transfered from repository to Fuser on mainframe:
„The Natural source code is temporarily saved in the Fuser file and cataloged. After the catalog process is complete, the source code is deleted from Fuser. This avoids possible inconsistencies between the source code in Fuser with the source code in the repository.”
It suggest I can’t use both editors at the same time.