I value the efforts you have made to inform us about this matter and for consistently assisting other participants in this discussion, Roland12. Allow me to provide you with the latest information regarding this situation.

After checking, the investigation about the inability to add or save attachments in the Bank Register with an associated number INV-101192 has been closed. You'll now be able to attach PDF file format within the register. You may refer to the images below: 

Furthermore, you can visit this article to learn more about the different file types and transactions that support attachments in QuickBooks Online (QBO): Add or delete attachments in QuickBooks Online. 

I remain prepared to support you if you have any additional inquiries regarding uploading files or documents into QBO, Roland12. I'll be available to offer guidance and walk you through the process step-by-step. Wishing you all the best for the remainder of the week! Stay safe and take care always!