>Are there any other text editors that have interpolated variable references?
The closest I can think of are Frescobaldi's snippets[1], vim's `!read`, or spreadsheets. Maybe light table [2]? I haven't seen anything exactly like what you've made
[1] https://www.frescobaldi.org/uguide#help_snippet_edit_help
[2] http://lighttable.com/