The Mark Loop tool can be used to add fine grained control to the Fuse tool.
A marked edge, will either forcibly be used to guide a fuse surface, or will be ignored, depending on the presence of other edges.
Marking loop edges currently just uses Blender's ability to mark freestyle edges.
In the future, I want to remove this tool and create custom manipulators for the fuse tool, which allow for more interactive loop edge manipulation.
Using Mark Loop
Use Clear Loop to 'unmark' loop edges.