When creating new topic, you can use tags which help other forum users to search by these tags all the relevant topics.
Using the tags is optional at the moment. Every user can add any existing tag to a new topic. Users with trust level 2 or higher can create new tags.
How to add a tag to the topic is very easy. Have a look on this screenshot.
Start typing in the optional tags field and the drop down menu will offer you the existing tags.
If you are a level 2 or higher user, you can create the tag in the very same field. Just type it in.
Tags are limited to maximum of 20 characters and each topic can be tagged with maximum of 5 tags.
If you want to see all the available tags, look at them in Trezor Forum.
Using Topics tagged transaction & rbf will give you the opportunity to filter the topics, which include all of the selected tags. Just type two different tags after the intersection/ divided by another / symbol.
If you use 
button, you can access an advance search, which allows you to search by tags as well.
