I cheated a bit.
I added some fields on the parent or root object, called Id and Value.
I used these 2 fields and changed them, then called an action, which a microflow picks up.
The microflow uses the ID field to find the object(s) I want to change using the value.
It’s ugly, but in my case it was a single string field on a child object I wanted to manipulate.
I tried a bunch of other hacks, but to no avail. I guess we’ll just have to wait for the feature to be implemented as of this writing
Making ListAttributeValue editable is part of our roadmap for the second half of this year. Currently, these values are read only. With 9.2 we improved the message and documentation.
Did you find a solution for this? I am facing exactly the same issue. When interacting with the same object but then directly as an attribute, hence getting back an EditableValue in stead of ListAttributeValue from the datasource, it does work...
After the time consuming process of creating a test project I filed a support ticket for this.