What does ‘Pop’ do?
That’s more or less an artifact in the menu from a system we called layer propagation you probably won’t see anymore at some point in the future. As it is right now a layer has a name and a color and they’re either used to define operations (when used top-level in a patch) or delegates (when used inside of regions). In the past (before the first public release) most of the nodes and pads in a patch where assigned to a layer automatically by propagating layer information up- and downstream based on user defined layer annotations.
Since that system lead to rather strange results during patching and also made certain future features impossible to implement, we decided to get rid of it slowly by using a different mechanism called active layer. You see the active layer you’re patching on in the top left window. Whenever you create a pad or node it will be annotated with the currently active layer. Using “Pop” you can remove that annotation and the layer will get computed from up- or downstream nodes as the kinda legacy layer propagation is still in place.
In short: It removes the annotation to which operation a node or pad belongs to.