Can the sprite editor slice two separate grids of different size pixels?

I have a spritesheet(PNG) with thousands of sprites that are 16 x 16 pixels and a few hundred that are 8 x 8. What I want to do is use one grid to slice the 16 x 16 sprites and another to slice the 8 x 8 ones. Can I do this or do I need to split the original image into two different files to accomplish this? Thanks in advance and apologies if I missed where this is already answered someplace.