I have got a category multi-select feature that allows users to filter variants by more than one category. On selection the URL is concatenated as a new category as follows:
?cat=blue ?cat=blue+decorative ?cat=blue+decorative+white etc
I am just trying to setup the paginate tag to show a list of variants that are filtering by the categories from multiple category fields that the variants have.
In this case they are 'colour' and 'shape'. There are discussions amongst the team about converting a multiple category group structure into a single nested category group to make functions like this easier.