Spawn new Tab instances from a TabManager

Hi, yeah I actually included a viewport without problems. As I stated in the answer, I used InsertNewdocumentTab.
About the ESearchPreference I quote

The search preference determines whether we prefer an open tab, or whether the tab next to which we spawn should be a closed tab whose location is saved in the layout.

There was a complete answer about this topic in UDN, am not sure that can be shared here.