I thought that categories or tags do not impact the actual display of the gallery (useful for searching purposes but do not determine the display). I am not sure what they are, so I am not sure how many categories I have. Maybe the categories are the species, not sure, you decide.
For the sake of the example, let's say that I have 100 species. Each species has a side by side display. In this display the left part cycles thru say 3 pictures and the right side cycles thru 4 pictures.
For instance the entry Coreopsis, will have 3 pictures of the flower in the left and 4 pictures of the print of the flower in the right. The entry Geranium, will have (the same to make it simpler) 3 pictures of flowers and 4 pictures of prints.
New video
Thank you.