Hi Jonathan,
Our apologises for the delay in implementing this feature. This feature is not completed yet. I have notified our development team and we will try to include this feature in our next release.
Feature Request # 206 - Ability to align the TabbedMDI tabs.
I have attached a sample that shows how to achieve this fuctionality with TabControlAdv.
Please let me know if you have any questions. Thanks for using Syncfusion products.
Regards,
Mano
TabbedMDI_TabLeft_1.zip