There is an old blog post for CMS 5 about this: http://labs.episerver.com/en/Blogs/Mari-Jorgensen/Dates/112298/112299/112384/
Haven't tested it in CMS6 but you should be able to do something similar.
Also, in the comments section of this blog, they mention a module which can hide pagetype tabs (e.g Categories): http://marekmusielak.blogspot.com/2009/05/episerver-hiding-workflow-and.html
Hi Team,
I want to show/hide or enable/disable one of my custom tab (made through pagetype builder) for specific pagetype based on some condition.
Is there any way with which I can do so in edit mode for specific pagetype. I have gone through this link http://labs.episerver.com/en/Blogs/Allan/Dates/2009/1/Neat-Trick-Modifying-Edit-Mode-Tabs/.
I am succeeded in applying conditions,checks for particular usergroups and for specific pagetype in custom plugin, but the mentioned code in a link only access the outer tabs like Edit, Preview etc.
Please suggest some wayout to access the custom tabs used inside specific pagetype.