It's possible to use insert file with a container field to open a dialog where the user selects the file from which to import records. The script inserts a reference to the file into a container field, extracts the path to the file from the container to a variable that you use with import records to specify the file from which to import.
The file can then be named differently each time.
To import from current file,
Set Variable [ $path ; Get ( Filename ) ]
Import Records [ $path ]
To specify import order, you need 2nd line for file path list as
2nd line is used only if $path is not found (when defining script step variable is not defined), so you don't need to change when filename is changed (until you need to re-define import order).
Yes, that second line is needed to retain the field mapping in the Import Records step.