I have a dimension that runs a tree farm, and it is chunk loaded, but it doesn't load with the server start so it doesn't do anything until someone enters it. Is there a way to have it load on server startup? Thanks!

It depends on the chunk loader. I believe Chicken Chunks works fine but some others don't. Also it can depend on how the chunkloader is configured.

ChickenChunks chunkloaders are only working because they don't use the ticket system from forge.
This behaviour comes from vanilla Minecraft and also happens if you log out in an RFTools dim: The overworld will be unloaded when logging in.

Would it be possible to have an admin command to add a specified dim to be loaded during server startup? Edit: My experience with chickenchunks is that it causes other issues to pop up and isn't 100% reliable/has some poor mod interactions.