(I'm on friendica.world.)
Settings → Addons → Content Filter (NSFW and more)
This addon searches for specified words/text in posts and collapses them. It can be used to filter content tagged with for instance #NSFW that may be deemed inappropriate at certain times or places, such as being at work. It is also useful for hiding irrelevant or annoying content from direct view.
→ check "Enable content filter", add stuff in the "Comma separated list of keywords"
both words and hashtags work.