The aggrid_diff sub module seems to now have basic functionality and works for a max of 3 header rows. In order to do this, I had to create another formatter type as a static HTML table. Instructions will be added on how to make it work, but it will involve adding a revision display view for this HTML formatter type. No errors/bugs were found, but I marked this as both a bug fix and new feature since it fixes aggrid_diff to actually work at a minimal level.
The formatter type will loop through up to 3 header rows and squash it down to one single header.
This is the first stable release of the Views Advanced Labels module.
The module is considered feature-complete and there are no known bugs (though some compatibility problems with other contrib modules – see #2882521: extend it for integration with some modules like).