Yes, this is possible. You must set MdiMergeable to False on both the parent and child toolbars managers. Then set the ActiveMdiChildManager of the parent manager to the child manager (or the MdiParentManager of the child to the parent). However, it sounds like you want to merge in multiple child managers into one parent, and unfortunately, this is not supported. You would have to do this manually by dynamically adding tools to the parent based on the loaded plugins.

I'm not sure if it has been requested already or not, so I cannot tell you if and when it will be available. You can submit a feature request here: http://devcenter.infragistics.com/Protected/RequestFeature.aspx. Also, even if you contact the support group and discover the feature has already been requested, I would still recommend submitting the request because the number of requests received for a particular feature is a factor in determining what gets implemented in each release.

I don't believe there are any examples of manually merging. I would recommend not trying to implement fully functioning merging though. Instead, when a plug-in gets loaded, determine which tools need to be added and just add them directly to the toolbars manager. When the plug-in is unloaded, you can remove the tools from the toolbars manager. Thinking about it in these terms and not in terms of merging may remove some of the complications associated with merging. Here is a help article on adding tools to a toolbars manager at run-time: http://help.infragistics.com/Help/NetAdvantage/NET/2008.1/CLR2.0/html/WinToolbarsManager_Create_and_Add_Tools_at_Run_Time.html