The Thickness slider sets the to add from the pop-up. The Split Masked Points button will split the selected SubTool into two separate SubTools, so that the unmasked part of as the plateau for Project of the mesh become separate. This will work with folder.
SubTools can be hidden by turning off the eye icon next to their name in the list, or all but the selected SubTool can be hidden by using Solo mode. ZBrush will now recalculate your subdivision levels and project the details onto the new mesh topology. This feature prioritizes your original polygon count over how many subdivision levels your model originally had. Each SubTool can be equal to the maximum number of polygons your system can handle.
