Action Parameters can be created in this way:-


Right-Click on Action in Keyword View
Click on Action Properties
Select Parameters Tab

***********Action input parameters*********
Click on "+" and add  the input Variables with their 
respective datatype and their Values

***********Action output parameters*********
Click on "+" and add  the output Variables(o/p Var name)  
with their respective datatype
Note- Here there is no Default Value tab 

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Once you have created Action Output Parameters
write in the Expert View of the same action
Parameter("o/p Var name")="pass"(you can give any values)

************
and then yopucan call this action in any other actions 
within same or different test

Passing the parameters from one action to another. Here is 
an example.
'Action1 script
dim var
var=Parameter("t")   'Input parameter
msgbox(var)

Parameter("a")=89    'Output parameter

Create anothere action action2
RunAction "Action1",oneiteration,"20",x
Msgbox(x)  'First action output parameter comes to action2 
automatically

Exit run