Back in Illustrator 15 and below, I believe this could be achieved in ADM using some undocumented dialog options upon panel creation, but know of no way to achieve this in Illustrator 16 and above. Illustrator manages panels that are grouped together (thereby showing as tabs) via workspaces, and there is indeed a workspace suite in the official Illustrator SDK, but I don't see any obvious way to manipulate grouped panels via the suite.
Even back in ADM, if you grouped the panels correctly at creation, the workspace the user created thereafter would override the grouping set by the plugin developer (which is to say that the grouping was only honored upon the first run of the plugin and ignored upon subsequent launches).
If you do any research of your own and figure out a way to make it happen via the official SDK, then please let us know so other forum users can benefit!
Even back in ADM, if you grouped the panels correctly at creation, the workspace the user created thereafter would override the grouping set by the plugin developer (which is to say that the grouping was only honored upon the first run of the plugin and ignored upon subsequent launches).
If you do any research of your own and figure out a way to make it happen via the official SDK, then please let us know so other forum users can benefit!