Add a Service to an Application, not General
To have an Automator Service/Quick Action show up in only a given application's Services menu, then in this case set, e.g.:
Workflow receives [Automatic (Nothing)] in [QuickTime Player]
      Note that [Automatic (Nothing)] is the default and can be changed as appropriate.
When setting in [QuickTime Player] the Automator Service/Quick Action will only appear in the Services menu of QuickTime Player, although it will show under General: in the application's Services menu.
It this case it will also show under General in: System Preferences &gt; Keyboard &gt; Shortcuts &gt; Services
As you can see in the pictures below, Say Foobar shows on the Services menu of QuickTime Player, but not Safari.

Example: