Hello Brian,
Q: I still don't have an answer to my fundamental question: where can I post a topic on this forum? I don't see a button or badge that says post new topic. All I can do is post comments or replies to existing topics.
A: In order to create a topic, you have to input your request first into the search line in order to check if the similar one exists already and then hit at "Ask a new question"
Concerning SDC-1200 labels. As we stated before, Shipping Integration addon does not allow to select this kind of label for printing.
However you can change the page settings of the label layout. Find "LabelTemplate.fr3" file at: C:\Users\%windows username%\AppData\Local\eMagicOne Store Manager for PrestaShop\StampsCache and find "Page Settings":
Then try to find the most appropriate page size: