Solution Part 1.

I have been able to figure out that printable Price List uses the ID of the first four Group Discounts as seen under Admin>Customers>Group Discount

Specifically IDs 1, 2, 3, 4.

If you still have ID's 1,2,3,4 (and have not deleted them having first added replacement ID's 5,6,7,8 - like I did, then you are indeed comparatively fortunate) - just edit the names to the reserved names e.g. Group A, Group B etc.

In my installation of Group Discount Per Item, I had added Group A Group B etc with IDs 5, 6, 7, 8 and once these had tested good, deleted the unwanted 'dealer, super dealer, tier1 distributor, tier2 distributor' discounts with ID 1,2,3,4. The result of having IDs 5,6,7,8 was that none of these were recognized by Printable Pricelist as valid IDs. So customers all failed PPList's security to view a price list regardless of the fact that they had a Group name identical to a name entered into Configure>Pricelist Profile 1, 2, or3 supposedly granting permission for a discount group to a specific price list.

Editing the Group Discount IDs directly in a text editor prior to re-uploading resulted in an unmitigated SQL disaster (not to be recommended). So I uploaded an old 'known good' database backup and edited the names next to IDs 1, 2, 3, 4, to the 'reserved names' Group A, Group B , Group C, Group D.

Well, now let's see if it is possible to produce a combined wholesale/retail pricelist (instead of a Incl. Exl pricelist).

Hmmm