Hello KVerwold,
Thanks for reaching out to us. Having multiple diagrams in the same EDMX file has been supported since EF5 and the version of the designer that shipped with Visual Studio 2012 RTM. To try it out, you can right-click on an entity or group of selected entities in a diagram and select the option "move to new diagram". You can also bring related entities to a diagram in a similar way. There are more details (and a video) about in our documentation.
Besides that, in the version of the EF designer we are working on now we have made a few performance improvements, so the designer can handle larger models with more responsiveness.
Hope this helps,
Diego
Thanks for reaching out to us. Having multiple diagrams in the same EDMX file has been supported since EF5 and the version of the designer that shipped with Visual Studio 2012 RTM. To try it out, you can right-click on an entity or group of selected entities in a diagram and select the option "move to new diagram". You can also bring related entities to a diagram in a similar way. There are more details (and a video) about in our documentation.
Besides that, in the version of the EF designer we are working on now we have made a few performance improvements, so the designer can handle larger models with more responsiveness.
Hope this helps,
Diego