CloudFormation SSM Parameters List

I can't say for the feature you're asking. But you could workaround this by maintaining the list with a lambda triggered which would "build" the list from a call to :

aws ssm get-parameters-by-path --path / --query "Parameters[*].{Name:Name}"

And store it in a parameter as a list already built to be used:

aws ssm put-parameter --name mb-tag-list --value $list --overwrite --type StringList

On update trigger a lambda through a Cloudwatch Event a lambda that get the list and update the corresponding parameter store.

I build it in a small shell script (but any language could work!) to prove that it works :

#!/bin/bash -x

list=$(aws ssm get-parameters-by-path --path / --query "Parameters[*].{Name:Name}" | jq -c 'map(.Name) | join(",")')

aws ssm put-parameter --name mb-tag-list --value $list --overwrite --type StringList