This feature request has first been part of my question here.
Currently I can either flag a post as Not An Answer or Very Low Quality from the main site, or I can review it Looks Ok or Recommend deletion from the low Quality review queue, if I have enough reputation.
However, I have no chance to determine if a post I see on the main site and find inappropriate is already in a review queue or not.
In case the post is in no queue yet, the action is clear and has to be a flag that puts it in the queue.
But if the post is already in the queue (which I don't know), I should rather visit the post through the review site and cast my review vote there instead of raising another flag.
As I understand it, flags do not count for the reviewing process other than raising the number of OK-votes that would be needed to remove the post from the queue again. So even if a post got ten (LQ, not spam/offensive) flags by users with enough privileges, that would not automatically make it reviewed.
I have two different proposals how this situation could be improved:
If somebody has the right to review LQ posts, his LQ flags (NAA and VLQ) should have the same weight and effect as a delete recommendation vote through the LQ review queue.
This suggestion has already been made and explained very detailedly by @Wrzlprmft here:
Make VLQ and NAA flags equivalent to a negative review in the LQ queue (if the flagger can access that queue)
I fully agree with his described proposal.
Or the user (with enough reputation) should be able to determine if a post they want to flag is already in a review queue they have access to.
Then they should get a link to directly visit it there and cast a review vote instead of a simple (and possibly useless) flag.
Alternatively they could also get a pop-up menu similar to the one for closing questions and directly cast their review vote from the main site.