An article called "A Spreadsheet and a Debugger walk into a Shell" [0] by Bjorn (letoram) is a good showcase of an alternative to cells in a Jupyter notebook (Excel like cells!). Another alternative a bit more similar to Jupyter that also runs on Arcan is Pipeworld.
I was thinking of Arcan and the Lash#Cat9 setup by the end of your second paragraph. I'm very surprised you had not met it: it seems so directly aligned with your interests and goals, but all you seemed to talk about was Jupyter, a tool which I tried and TBH discarded after 10min.
I talked to Bjorn Stahl quite a bit before writing it, but he is so smart he seems to me to find it hard to talk down to mere mortals. There's a pretty good interview with him on Lobsters:
