Hi Pavol,
Thanks for contacting Syncfusion support.
RibbonControlAdv Tab and TabItems can customized in run time using Ribbon Customization window. Ribbon Customization window can be opened by right clicking on the Ribbon and selecting Customize the Ribbon or by clicking the dropdown button in Quick Access Toolbar and selecting More Commands option. Following that, you can create multiple ToolStripEx groups and then add the same buttons to each group. We are currently testing the similar scenario by adding the buttons using Customize the Ribbon in the Designer. We’ll check and provide the further details on January 21, 2021. We recommend to add the button to the ToolStripEx groups at run-time.
Please refer to the attached videos from the following location:
Please refer the following screenshot for your reference.
Could you please try the above solution and let me know the reported issue has been resolved or not. Please let us know if you need any further assistance.
Regards,
Thirupathi B.