HI Paul --
Yes.Registering any version of a UserActions script will replace the previous.
Yes, only one UserActions can be active at a time.If one wished to incorporate features such as this into an exisiting modified version of UserActions, one would have to merge the code?
Yes, that is the purpose of the #waitxxxx directives:could #waituntil be used as a rudimentary way to add some 'timing' to each target in the plan?
As always, this is a roadmap to the info not an "RTFM" criticism :-)