Hi Vlad,
We have added a new feature 'Custom Caption Buttons' with 5.1 version. This allows user to add new caption button. You can find more about CustomCaption button from the following link.
http://www2.syncfusion.com/ug/Default.aspx##Essential%20Docking%20Windows.chm/CutomCaptionButtons.htmlBest regards,
Poly