Vladimir

And what if I would like to have 1 common FormTab? Now, if I have 1 FormTab in general config it doesn't display if I choose FormTab config, so I...

This code should output list of galleries with their first image as thumbnail.

ok, the problem was cos i set basePath in mediasources as "[[migxResourceMediaPath? &pathTpl=`assets/resourceimages/{id}/` &createFolder=`1`]]" (as it's said here https://rtfm.modx.com/extras/revo/migx/migx.tutorials/migx.use-resource-specific-media-source-and-multifile-uploader) solved the problem by setting it non-cached "[[!migxResourceMediaPath? &pathTpl=`assets/resourceimages/{id}/` &createFolder=`1`]]"