At QGIS 3.4.7, I have some polygons that are overlapped and I use Polygon dissolver (by attribute) from SAGA to dissolve then and I check the option "keep inner boundaries", but this tool takes too much time to run.
I need them that way for the Check Validity to point to the overlapping location.
So, Are there any other way to dissolve the polygons and keep the inner boundaries to gain some time? The native Dissolver and GDAL´s don´t have that option.
EDIT: Example of inner boundaries in a single feature