Interesting; you’re describing something like Excel’s PivotTable function, but for hierarchical setups. Challenging!

Many of us are still mourning the untimely death of the hierarchical outliner par excellence, Tree2, which – while it didn’t do PivotTables as such – could extend outlines horizontally as well as vertically. The resulting flexibility was unprecedented. Dashword (also macOS) is a more recent attempt to do more or less the same thing, and is worth a look, not least because you can organise your horizontal outlines in named columns (they disappear in “vertical” view, but reappear when you switch back to “horizontal” view).

Cheers,
Bill