Hello,
Here is the tutorial on how to protect your personal tags: How to Protect Personal Tags from being Overwritten
Just a quick reminder: the only way to add new cards to a filtered deck is to rebuild it, which resets the deck. So, if you added tags to new cards and want them to be included in an existing filtered deck, you must click the “Rebuild” button. Unfortunately, this is a limitation of Anki.
Let us know if you need help with anything else. 