You can do this via a java action. But without java, there is no such action in microflows.
You would need to drop to Java to do this.
Have a look at Community Commons, there are various actions to execute microflows there that may do what you need.
If not, look at Core.execute. This takes a context, a string with the microflow name, and LinkedHashMap of parameters to pass into the microflow.
Hope this helps!
Unfortunately, this isn’t possible on microflow level.
Thanks Guys. Java looks like my only choice.