Dependent lists/Indirect and multiple workbooks

Hi all - first post here and any help is appreciated.

I have 4 separate forms (workbooks) set up that have multiple dependent dropdown selections using data validation and the INDIRECT function and also using VLOOKUP to access other data based on the selections.

In each of the 4 forms, I have the named lists/table on a hidden separate worksheet in the same workbook. Now, the department using these wants to be able to just have one master workbook to update rather than having to do the hidden sheet on each of the 4 forms.

I've discovered that INDIRECT apparently cannot reference a separate workbook unless it is open. Ultimately, these 4 forms (and the source workbook) will be stored on a shared drive for multiple managers to access and use (the source will be psswd protected). I'm trying to figure a better way to either set up my table so I can use VLOOKUP only or to get around using INDIRECT for my data validation for the dependent dropboxes.

I am sure I am missing something very simple, but I'm pulling my hair out here. I thought I had this all wrapped up (and I'm impressed I got this far!!) I'm attaching a fictional example of the potential source data workbook. On the 4 forms themselves (separate workbooks), the first cell would have a dropbox with the DEPARTMENTS (from data validation), the 2nd cell should have only those positions corresponding to the DEPT selected (currently done with INDIRECT using named ranges), and the other cells should auto-fill based on the selected position (currently done with VLOOKUP).

Like I said, I've got it working perfectly now, but I can't figure the step of moving the source data to a separate workbook. THANKS SO MUCH for any advice.