when you want to hide a buff you type /bh buff Buffname in chat (case-sensitive) and type it again+reload ui if you need to show it again
when you want to hide a debuff you type /bh debuff Debuffname in chat (case-sensitive) and type it again+reload ui if you need to show it again
when you want to list all hidden buffs you type /bh list in chat
when you want to see how to use it you type /bh in chat
currently does not hide short duration buffs and no idea why