Problem summary: in many cases we need in grid to show custom fields at window or window customisation level. ATM we have A. Virtual DB - not recommended because performance B. Virtual UI would be ok, however not rendering in grid, and not possible define at window customisation level.
*Potential Solution, POC: *
Similar like info window add to ad_tab and ad_userdef_tab field - select clause field, then another required field to ad_field or ad_userdef_field - to achieve the same approach as on the info window.
*TODO: after code analysing define exact technical solution concept. *