Q: Is there a way to toggle this setting (wise lister gallery on/off) when listing bulk?
A: In Wise Lister - Gallery On/Off just means to select/deselect all of the images to include them or exclude them from being uploaded in the eBay images. You'd have to at least have 1 image selected, but users wanted a quick way of selecting and deselecting all so that they could go back and choose individually a bit easier. When listing batch listings, all of the images would be included (up to 12) as that is the max allowed by eBay. If there are more than 12 images, you may get an error from eBay because you've exceeded the max.
Note: You can't edit that setting when listing in bulk and if you did turn it off, then your listing would attempt to upload without even 1 photo - which would cause you an error in eBay -- eBay would tell you that you need to add at least 1 photo.