How to create a surface from line selection

I have split two body in diagonal and I would like now to seal the opened area by a face. More simply put, how can i create a surface to seal a shape by selecting surrounding lines?


Either create a flat plate and align it to the face you want and split body to trim, or extrude the face you want to close then offset faces to close that shape to a closing plate.

I may not fully understand the use case, but sounds like the Split Body tool combined with the Replace Face tool could do the job.