If you’re still looking for a solution I would recommend our Ablestar Bulk Product Editor. If you’d like to edit the tags in descriptions in bulk (like add a tag to all products matching a condition) you can do that with an in-app edit:
You can also upload a spreadsheet with your tags and descriptions and update your products from that (unlike in the Shopify Admin you can see the progress of your edit and undo it if necessary)
We also have a free plan of 5 edits/month (with no limit on the number of products) which could be a good fit if you’re just wanting to make a few fixes.