SCMDraft 2 String Editor, isn't used to actually create Triggers as such, but gives out a view of all the Strings currently used within your map, which you can self-edit within that.
This includes, wav's, any names of units you've changed, displays of text in the triggers, and mission briefings, forces name, name of map and locations.
It isn't possible to really create new ones and use them, because they don't have a "pointer" and just waste your space.
Don't use SCMDraft 2 for triggers, use X-Tra Editor or else use the Text-Based Starforge Trigger Editor.