I read the documentation and searched in this forum, but found nothing. How can I create a custom renderer for the DockPanelManager? The DockPanelRenderMode-Enumerable supports this option..
The API required to set a custom renderer is not public. It was originally planned to make the required types and members public, but there seemed to be no demand for this kind of feature, so we skipped it.
However, if you purchase a license you will get the full source code. You can simply customize an existing renderer or add your own.
How can i add a contextmenustrip to the tab-header?
You can set a ContextMenuStrip using the DockableForm.TabPageContextMenuStrip property. Check out the included SampleApplication.
document.TabPageContextMenuStrip = _contextMenu;
The context menu will be shown when the tab-header is right-clicked. Right-clicking the empty space in the tab-header panel will also show the context menu of the active document.