In a Workflow: does anyone know if it's possible to check a sublist column to see if the values equal a specific value for all lines? I found this blog post online but I was unable to achieve the desired results after testing in our SB environment. Ultimately I have a sublist column on a Sales Order, and I want to trigger a discount WF only if the value in the column = PROMOTIONAL for all lines.

I haven't worked much with sublists in workflows, but there is another angle you can try if you need to do this in a workflow. You can create two custom fields sourced from summary saved searches - one that counts the total lines on the record and the second to count lines matching the condition you want to check. The workflow would then need to check if the two fields have the same value.