How to unpulish the Mac version of an iOS app?

On App Store Connect, the iOS and macOS versions are published separately.
So you can choose one of them, and remove it from sale.
The other version is not affected.

Go to "Pricing and Availability" > "Availability"
Select "Remove from sale"
"Save"

(There may be a delay, before the app is removed from the App Store)

The issue is that for me both are in one:

When you hover the mouse over the macOS-App "1.0 Bereit zum Verkauf", do you see a red "-" (delete) button?

From https://help.apple.com/app-store-connect/en.lproj/static.html

You can delete a platform if a build has never been uploaded for the platform you wish to delete.
Additionally, at least one existing platform version needs to be in an editable app status.
See App statuses.
If the criteria is met, hover over the platform you wish to delete and click the delete button (–) that appears to the right of the platform.

This is slightly confusing, but it works...
There must be an editable version for another platform, for the delete button to show up.
Like this (1.3.11 for iOS is editable, so I can delete the macOS version):

Then the macOS version can be deleted.