Edit
Collections opens the list. Add collection appends a row. Save writes the list into the Graph draft (autosave).
At most 32 collections. A name already in the list cannot be saved. Schemas that are too large cannot be saved.
Under Import from Instance, choose an Instance and press Import. That copies names and schemas, not records. A matching name replaces that row. Remove rows you do not want, then Save.
Removing a row does not delete records already stored on an Instance.