It seems like many plugins are one .cs file but if the plugin becomes large it's very messy. For this reason I want to produce a DLL with a plugin class and then all the other classes it uses.

So anyway, I'm wondering if Oxide can reload plugins when it detects a file change for the DLL (or via the console command) like it does for .cs plugins?

You cannot hotload dlls uMod Docs

Ah thanks, I already suspected it as I thought I had read it before. Do you have any suggestions on how to keep it somewhat organized? I guess using a lot of regions in the editor can help :|

Oxide does have basic hotloading of extensions (not any DLLs), but you can also reference external DLLs by using "// Reference: FileName" at the top of your plugin. Keep in mind that the reference method would only be for private plugins, as any DLLs not bundled with the game aren't distributed via our site.

Another method would be the "// Include: FileName" option, which you would also place at the top of your plugin. In this case, a file would be created under oxide/plugins/include that contains the classes you'd like, then you'd simply call methods and utilize it as you normally would any other C# dependency.