It would be nice if the primary tags were all expanded by default (in the image above, only the 'Feedback' tag is expanded). Currently the only way to see the full list of tags available is to either visit the 'Tags' page, or manually clicking through each tag one-by-one to see the available sub-tags.
This makes it difficult to get an easy idea of the structure of the forum. e.g. "Was 'Themes' under 'Extensions', 'Resources', or 'Dev'?". We have to try and remember each sub-tag ourselves. It also means one extra click to get to the tag I want. That may not sound like alot, but when your users are using the forum very frequently, it can get a bit tiring.
For new users (or even familiar ones) wanting to quickly find/create a post with a specific tag they vaguely remember the name of, it's rather time consuming to have to click through each tag until they've found the one they want. It would be really nice if all primary tags also listed their sub-tags.