Hi Abinav,
Thanks for the evaluating Syncfusion Essential Studio WPF Tools. I was not able to reproduce your issue. Please see the attached demo sample. I have created ribbon window with TaskBar Inside of the RibbonWindow. Seems it will meet your requirement. If it's not meet your requirement please provide one simple sample for further investigation to meet your requirement.
Please let me know if you have any questions.
Thanks,
Venugopal.
Ribbon.zip