Hi
Qihhh,
Thank you for using Syncfusion Products and Sorry for the delay in getting back to you.
Currently it is not possible to set something on close button in Document window which is present in Docking Manager by directly, but it is possible by some workaround.
We have prepared a work around sample for your requirement and you can download the sample from the attachment.
In this sample, we have modified the CloseButtonTemplate for both Selected and UnSelected tabitems in Document Window. Then modified templates are used in DocumentTabItemStyle, because that style is needed for changing the behavior of TabItems in Document Window.
Please let us know in case of any queries.
Regards,
Muthalagu
CloseButtonStyleInDockingManager_523c3fbb.zip