When importing polygon based seamlines to mosaic pro from external shapefile. "Error – Image attribute for does not exist!"
Creating external seam polygons file outside of Mpro is difficult. You can still create your own seam polygons manually. You will need to assign the appropriate image as attribute for each seam-polygon manually. If it is not properly done, it will not work. An easier way would be first generating sample seam-polygons file from MPro, save it as *.shp file, load that in IMG Viewer and check/review the vector attributes attached to each seam-polygon. You can create your own seam-polygons as *.shp file, follow the example, create and attach these image-attributes manually, load that in Mpro and re-save it as Mpro generated *.shp file. When you use it, be sure you will have exact images loaded in Mpro, nothing less, nothing more. Hence, it seems to be easier to edit the MPro generated seam-polygon file than creating one manually.