Seems to be a lot of issues with the filtering.
I’m trying to use the:
has:blue-info
filter, or any filter that will look for the various stars that can be applied in gmail: yellow-star; blue-info, etc.

none of them seem to work.
thanks in advance to anyone that can help point in the right direction.
Just ran some tests, I can confirm that:
The module:
- does not return results for
has:blue-info
- does return results for
is:starred
When searching from gmail search, has:blue-info
does return results.
I would contact support on this.
thanks for confirming.
apparently, this is not high on their priority list… 
The problem is that the flags names cannot be used in the Gmail API, you need to use the following code:
has:yellow-star <=> l:^ss_sy
has:blue-star <=> l:^ss_sb
has:red-star <=> l:^ss_sr
has:orange-star <=> l:^ss_so
has:green-star <=> l:^ss_sg
has:purple-star <=> l:^ss_sp
has:red-bang <=> l:^ss_cr
has:yellow-bang <=> l:^ss_cy
has:blue-info <=> l:^ss_cb
has:orange-guillemet <=> l:^ss_co
has:green-check <=> l:^ss_cg
has:purple-question <=> l:^ss_cp
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