Cascade - Grouped Modules

Hello all,

 Sorry if this is a waste of time question, but I'm looking at some modules in Cascades Particle system and I noticed that some modules have a ' + ' next to it, and appear to be grouped together.  I can't seem to find the button or option to group one module from one emitter, to another module in a different emitter [sample picture here].  So my question is, "How do?  @.@"

Also, what exactly happens or is the point of, grouping modules with one another ?

UPDATE: Figured it out [Face Palms]

for other people stumbling across this thread - shift-dragging a module to another emitter creates an instance of that module. changing values in one of those instances updates the values in all other instances.

How can you ungroup module? I can delete module and recreate and this work for most of the modules but not for required modules like Spawn.

there may be a better way, but you can also ctrl+drag from another emitter to just copy the values without making an instance.