Export Mark layer to shapefile

I create an NDWI mark layer and intent to export as shapefile to edit by Qgis but I only can export to xml file.
please help me to open this file in Qgis
Thank so much.
Tuan Anh

This is currently not possible.
A vectorisation of masks is not yet implemented.

Thank you so much for your information.
Yours Sincerely,
Tran Tuan Anh