It’s not possible to change the default script location. When you execute the dms script, the post migration step gets invoked and the script location is based on where your PS_HOME is defined in stat. For example, in User Options | Peoplesoft Options, I defined the default pstools directory which is PS_HOME\bin\client\winx86. Now if I click on the run button, the DataMover Variables window will be displayed and Stat will append \scripts after the PS_HOME location. (see screenshot attached). Perhaps you could map the scripts location to a drive letter and then all you'd have to do is click the folder icon to browse to the location with just one click.
The ‘\script’ subdirectory can only be changed at the time of execution.
From the Sys Admin guide, page 148:
Run DataMover Script (PeopleSoft Only) When this step is triggered, Stat logs in to the PeopleSoft environment (by default, the target environment of the migration) using the user’s PS operator ID and password and runs the selected Data Mover script. By default, Stat uses the .dms file in the subdirectory “\script,” which is appended to the PeopleSoft Home Directory (PS_HOME) defined in the PeopleSoft Configuration Manager. All of these settings can be changed at the time of execution.