How to configure milestone with some action in record ?

We have no idea how your application logic looks like. So the only hint I can give is something like "Add a button to the interface which modifies data in DB". Not sure whether that helps.

Please elaborate.

i want to add action called "Approve Request" in record, after clicking on action the milestone bar come to completed. Is it possible, i want to do it from record type not from interface.

You can add a button or icon as a column into the record grid.

yes, But what is the logic behind  the button ?

See my first post. It is your application ...

But in general, that button can use a!writeToDatastoreEntity() or a!startProcess() or instead of a button, use a link and a!startProcessLink()

Thanks