See the answer to this forum post: https://forum.mendix.com/link/questions/93070
Hope that helps,
It is not possible, like Mike says. You need to create an Object containing that content and references (and thereby cluttering your domainmodel) and retrieve it. Mendix is limited in passing values and objects from a page to a microflow.
There are already several ideas for improving this, ‘choose your object’ (implemented in 7.19), ‘passing primitives’ in ideas 100, 174 and 1170, planned to get implemented since feb 2018. So it might help to create an idea for this.