Hi Dima, you’ve been busy! I’ll have a look at whether I have exposed a global import Filter but it may need to run several times as we use the WP-AJAX engine within the WordPress Administration and it may be treating each part of the Product import process (Populate Products or even Populate Product #1) as a separate request which requires those Filters to be re-applied on each new request.
If you were using the CRON import engine it could be applied globally as it’s a single request. I’ll clear my wall of Support tickets and reproduce this with you then respond here in detail 🙂
