Hi,
Let's organize a quick skype call, it will be simpler.
1: all ecosystem actions are on public github repositories, so updating you actions means you need to clone these repositories, modify the action, and then commit and push your change back to the repository online
2: You can reference dependencies within action to link other files ( like custom inspector, classes and in your case shaders), or you can make a package of this action +shader and distribute on the ecosystem that package instead of the action, but for actions I suggest you study the dependancy system, it's easy, check out for example the action ScreenTo3dPlanePoint.cs:
// (c) Copyright HutongGames, LLC 2010-2014. All rights reserved.
/*--- __ECO__ __PLAYMAKER__ __ACTION__ ---
EcoMetaStart
{
"script dependancies":["Assets/PlayMaker Custom Actions/Camera/Editor/ScreenTo3dPlanePointActionEditor.cs"]
}
EcoMetaEnd
*/
3. adding more actions requires to have the clones of the repository it should go ( Unity 4 and up actions goes in the U4 rep, Unity 5 and up goes in the U4, etc) check with me on what action you want to add, and I'll help you choosing the right one, once you understand the principle, you'll be fine.
Bye,
Jean