What would make this even better is slide the layer to the position you wish to split. Then click the split wizard then have the z-value pre-populated with the layer you are at with option split above current layer or below current layer. I find myself splitting it then making adjustments to two processes till I like the layer it splits at. This can take a lot of clicking... to edit process, select the tab, change a number click okay. choose other process, click a tab, change a number, click okay. Test slice. Repeat if necessary...
like the idea of a split wizard but wish it was possible to do by layer... somehow. I know this can be complicated if there is varying layer heights