Cannot build standalone version with my custom DLL

Does anyone what is the problem?

It works fine in Unity Editor but just Failed when building a standalone version Unity 2019.4

 ArgumentException: The Assembly UnityEditor is referenced by ModularMotion ('Assets/Plugins/ModularMotion.dll'). But the dll is not allowed to be included or could not be found.
 UnityEditor.AssemblyHelper.AddReferencedAssembliesRecurse (System.String assemblyPath, System.Collections.Generic.List`1[T] alreadyFoundAssemblies, System.String[] allAssemblyPaths, System.String[] foldersToSearch, System.Collections.Generic.Dictionary`2[TKey,TValue] cache, UnityEditor.BuildTarget target) (at <af78ad00a40d4f61b82afc6cafb0a416>:0)
 UnityEditor.AssemblyHelper.FindAssembliesReferencedBy (System.String[] paths, System.String[] foldersToSearch, UnityEditor.BuildTarget target) (at <af78ad00a40d4f61b82afc6cafb0a416>:0)
 UnityEditor.EditorApplication:Internal_CallGlobalEventHandler()

Please Help! Thank you