AFAIK a variable has no TAG property (only fields and tables have it). A COMMENT property exists but it's not available from the script else only from the UI. In QlikView the variables-comments could be read/write per macros. In Sense it should be also possible with any API but I don't know which and how.

Beside this you may load your Excel directly within the data-model and providing the information in a table to give the users additionally insights.