Can't add more tags to a topic, and not all are shown in the dropdown?

[merefield (Robert)]

@Airw0lf

there are posts which don’t allow adding more tags.

Presumably you mean Topics as you can’t tag Posts.

Also you might have reached the max, but there’s a setting:

I suggest you familiarise yourself with the settings in the Tag section.

/admin/site_settings/category/tags