A lot of this text [describing MACRO per se] can be moved to the core message_ix docs, given that many of the operations are consistent across any implemented MESSAGE[-MACRO] model.
This will require two linked PRs:
[x] One on this repo, removing these sections and replacing with an intersphinx link to the correct section of the message_ix docs. —#51
[ ] One on message_ix, adding the corresponding sections.
As suggested by @gidden on #27 by @volker-krey:
This will require two linked PRs: