Pinning to the Dock
Keep a Linux app in your Dock, like any Mac app.
Pin to Dock — the pin button on a tile, or the right-click menu — puts the app in your Dock. Unpin from Dock takes it out.
Pinning needs a real Mac app to point at, so if the app isn't in your Applications folder yet, MSL adds it first. Pinning implying "add" is less surprising than refusing.
Unpinning never starts an instance. Pinned apps work with the MSL window closed.