Add, remove or replace tags

Tags are replaced, not appended. Whatever is in the cell becomes the product's complete tag list, so always start from an export that already contains the current tags.

Adding a tag to a selection

1. Export Products with Handle and Tags, filtered to the products you're tagging.
2. In a working column: =IF(ISNUMBER(SEARCH("sale",C2)), C2, C2 & ", sale") so you don't double-add.
3. Paste as values over Tags, delete the working column, import.

Removing a tag

Use find-and-replace on the Tags column: replace ", sale" and "sale, " with nothing, then tidy any cell where the tag was the only one. Import the result.

Renaming a tag everywhere

Export filtered by the old tag, find-and-replace the old name with the new one, import. Smart collections that reference the tag pick up the change automatically.