An action button inside of a Listview can have 0, 1 or 2 parameters. The parameters that can be passed to the microflow are the object you are on (the row in the ListView) and the enclosing entity of the ListView (if the Listview is enclosed in a parent entity, for instance inside of a Dataview). You cannot pass the list of all objects in a Listview to an action button inside of the Listview.
As Austin suggested, you could have the Save button outside the Listview and retrieve the objects in the Listview again and then commit them. The potential issue with this approach is if you retrieve these objects from the database using XPath (as opposed to using an association), you will lose the changes that have been made.
Another approach would be to create a small microflow that commits one object of the type you have in your Listview. Then make that an onchange microflow for each of the input fields in your Listview (text boxes, radio buttons, etc.). In this way, changes will be saved as you go along, and you won't have a need for a Save All button.
Hope that helps,
Instead of having your microflow accept parameters, can you retrieve the list again? The same way you are retrieving your list in your data source microflow.