Hi Lorenz,
Thank you for using Syncfusion Products,
We would like to let you know that currently in ribboncontroladv we do not have tabs with the same name. Due to this behavior when the tabs are merged the tabs get added to the parenet form with the same names and not getting merged if same tab name is encountered. We have made a workaround for achieving your requirement which is available in the below link.
Sample: http://www.syncfusion.com/downloads/support/directtrac/124154/RibbonControl-1143556664.zip
Please have the sample and let us know if you have any other concerns.
Regards,
Ashwini