This can be done using the Serenji extension. Free evaluation keys for Serenji's debugging features are available on request.

The steps are documented here. I demonstrated it on the main stage at Global Summit 2019 during a session hosted by @Jeff Fried but unfortunately the YouTube video of that session has since been set private (see item 10 at https://community.intersystems.com/post/intersystems-global-summit-2019-... for the link).

Stefan, it sounds like you could benefit from using the server-side editing capabilities of this extension, in combination with server-side source control such as Deltanji from George James Software (for whom I work). Properly implemented, server-side source control will also control people who edit using Portal and Studio, or who use our Serenji extension for VS Code instead of the InterSystems one.

That setting affects how the ObjectScript Explorer behaves. That's the tree you get if there's an InterSystems logo on your Activity Bar and you click on it. It's the tree whose primary purpose is to let you export server code into files on your workstation that you then edit locally, probably add to a Git repo, and import to your server to run and debug it.

When you select a class or routine in that tree, and it only exists on the server (i.e. it isn't one that you have already exported locally), then the above setting dictates whether the code is opened read-only or editable.