You may be missing some setting in the Build.cs file for your module. I’ve definitely had to add to the PrivateIncludePaths there, but only for a Private subdirectory. I’ve never added one for a Public directory.
The editor plugins are a little weird because they add a bunch of extra optional layers on top of the Source directory. Under /Plugins you can have whatever structure you want. Eventually you’ll have a /Source directory which contains Module directories which should have Public and Private underneath along with a build.cs. From there you can do whatever you want again. And you should be able to include from the part of the path that comes after Public or Private no problem.
Do you have any difference between your own files and includes from other modules that you’ve included in the PublicDependencyModuleNames or PrivateDependencyModuleNames?