How to best add a "CMIP7-harmonization" tag for a specific list of emissions variables

[jkikstra]

I would like to basically implement tags for a variable list very similar to what is available here [sheet: IAMC variables].

I would like to create a meta column "CMIP7-harmonization" with the options: "global" "regional"

These should apply to a list which is a combination of species and sectors. It is possible to update it later.

I'm wondering how to best implement this, without messing up the current "Level-1/2/3 species" structure.