If I missed tabbing/indenting/spacing a line, is it possible to grab that line and all “sub-lines” nested beneath it, and indent/outdent all at once?
Yes. Select the line and those below. Indent them with tab and de-indent with shift and tab.
The normal Rhino 7 editor preserves indentation under this. However if the indentation was incorrect, i.e. with an extra space in there, this won’t correct it unless you remove all indentation.
Gah, of course. 
Thank you.
Also (of course, now that I finally asked) I see the right-click dropdown with “Selection → Indent”