I've seen the usage of English phrase for what it's worth many times.
However, I still don't know what the most precise translation of this phrase is in Russian.
No direct translation exists. 'For what it's worth' usually means that whatever is to follow is going to be a subjective opinion, which translates well to
If you want to communicate that a piece of information is potentially unimportant for another reason, you could say something like 'Может, это неважно, но'.