I believe calling a refresh on the entity of the list in a java action would do.
All you need is an object of the entity of the datagrid.
One option is to keep a separate object that has a reference to the object that's in the datagrid. The microflow that you're calling can then adjust the referenceset and commit with "refresh in client". Add the datagrid to a new dataview with the "hidden object" and set xpath constraint to the relation.
Not very pretty but it should work.