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.
Nox---soft-office

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?