Deselecting sub folders in a nest of folders


Please remind me how do I deselect a folder in a nest of folders?

I have a “root” folder called All Photos that is Boxifier selected. From this I have +100 of sub folders. My Canon camera download app collects all photos into individual dated folders deep in the nest, two of which have several hundred photos of time-lapse shots. It is these two folders I don’t want to upload to Dropbox.

It must be a simple right button click somewhere!

Thanks for help from someone!