Volumes/surfaces between polysurfaces

New to Grasshopper; I successfully created a branch of open polysurfaces (see screenshot) with the physarealm plugin.

I am now trying to build volumes between certain branches, similar to what’s shown in the Soft Office design of Lars Spuybroek, see picture.

Is anyone able to help me guide to what grasshopper commands I need to use?

Attached the gh file I created
gh file.gh (17.5 KB)

Anybody got ideas/auggestions what I could try?