Save an action to reuse

You have at least two choices:

  1. Put the Action by itself in a macro, and call that macro when needed using Execute a Macro action (KM Wiki).
  2. Use the excellent system by @DanThomas to save and insert Actions in a macro when needed:

I actually use both methods, but use #2 the most often. It is particularly valuable for creating macro and/or Action sets as templates – which using Execute Macro is of no use.