Which other compositions can access a subcomposition
installs the subcomposition in a Composition-Local Library. This makes the subcomposition appear in the Node Library only when the composition it came from (or another composition in the same folder) is open. If you want the subcomposition to appear in the Node Library for all compositions, click on the subcomposition window and go to .
For an explanation of Composition-Local and User Library folders, see Installing a node.