I haven't had time to look at this since and it's very important to me to get this working.

Does anyone know if I can do this without creating new UDFs, but using the existing ones? Can they be modified -if that's even necessary- to get information from the Sales Order Entry into this new tab I've added in Invoice Data Entry, so the data can be seen here and will appear in a sheet that's generated using the buttons here? 

I looked at the help files that are included in Sage 100 Standard ERP 2013 (5.00.9.0) and only found these help files, which didn't seem to be exactly right, but I looked at them anyway, particularly the one that's highlighted: 

i.ibb.co/.../Screen-Shot-2020-10-12-at-9-48-34-PM.png

Now, I enjoy chasing wild geese as much as anyone else trying to run a business in California, but can someone at least let me know if I'm on the right track?

I noticed this as well - probably way off, but who knows. Maybe it would help me. The goal here is to bring information from the sales orders into the new tab and generate a document of some type (PDF, Excel) so the files can be sent using the button I created, or emailed/uploaded separately if I don't manage to get the buttons working, which is going to be another quest, I'm sure.

Look at the entries for Invoice to AR Invoice History, that will tell you how to take from SO Invoice to AR Invoice History

Look at the entries for Invoice to AR Invoice History, that will tell you how to take from SO Invoice to AR Invoice History

The question / process is a bit complex and to do planning, add UDF's, customized panels and come up with a custom report is 1-5+ hours of billable work (depending on the reporting strategy).  Most of this stuff does not have step-by-step instructions, so perhaps break things down into smaller questions?

Perhaps start with the reporting strategy, because depending on direction there, the requirements for UDF flow can be different.

I think this was probably what was needed to get this moving - I ended up using new UDFs instead of trying to save time having data imported automatically. The shipping clerks can enter the data in manually and I won't lose any sleep over it.

I've hardly had time to work on this since I started trying to get this setup, but this is what I've got after attempting to deal with this tonight in another way than I originally planned: 

The buttons aren't functional - I haven't done anything with them yet, but now it's time to figure out how to work with the data in this tab and export it, so I created another post about that task alone.