AWS SSM Parameters - How to expand lists within Allowed Values

Hello,
This question is referencing a thread kidnap that was never answered here:

https://forums.aws.amazon.com/thread.jspa?messageID=982615﹗

By user longman

And taking it a little further.

If I can export the Resolved Value of a AWS::SSM::Parameter::Value<List<String>> SSM parameter by doing:
Parameters:
Test:
Type : AWS::SSM::Parameter::Value<List<String>>
Default: List_of_Values
Outputs:
ParameterList:
Description: The first CIDR block of the Parameter Store value
Value: !Join [ ",", !Ref Test ]
Export:
Name: ParameterListString

Why can't I use that Parameter List to Resolve to a list in Allowed Values?
Parameters:
Options:
Type: String
AllowedValues: !Ref Test
Is a very basic use case, displaying a SSM Parameter as a list to the user when running the Cloud Formation stack. Why is there no documentation in AWS about how to do this. Not in the Official AWS blogs, not in the support documents, not in the AWS CF Manual, not in third party blogs. NOWHERE there's an example of using AWS::SSM::Parameter::Value<List<String>>.

Please provide one that is not as obvious as Importing the parameter and then using it as a Resource Property, we need the use case where a StringList SSM Parameter can be converted to a List in AWS for a user to choose a value from. Thank You!