If you want to disable the stock ship designs permanently try this mod I made to do just that http://www.nexusmods.com/galacticcivilizations3/mods/39/? . For obvious reasons the AI still make use of the core ship designs.
I was actually so frustrated by the clutter and constantly clicking the 'Obsolete' button that I made a mod that disables the default ship designs for all the vanilla races, the AI still use them obviously. http://www.nexusmods.com/galacticcivilizations3/mods/39/?
I agree that having a way to disable the default ships designs would be nice. I was actually so frustrated by the clutter and constantly clicking the 'Obsolete' button that I made a mod that disables the default ship designs for all the vanilla races. http://www.nexusmods.com/galacticcivilizations3/mods/39/?