Concerning optional parameter, UI of the Execute Macro Action can appears in three basic forms:
1.
2. 
3. 
Feature requests:
For a new action, to have user choice (perhaps hidden setting) of default initial form between 1. and 2..
For a reference to an already existing macro, automatic choice between form 1. and form 3. depending of existence of a token %TriggerValue% in the body of the referenced macro 
-Alain
A way to do this right now is to use a Named Clipboard. See:
In the future, I have a full-featured macro set coming that will make it easy to create lots of different customized actions.
Thanks Dan for recalling your interesting video
@peternlewis This tip will help untill feature request 2. will be implemented 
Looking forward for your named clipboard snippet "full-featured" manager 
-Alain
Noted.
This is done for the next version.