I found this thread that should be of use to you: Why does BindKey cause Link error? - #2 by Pierdek.
It seems that you need to include some dependencies in your project.build.cs file, which is labeled as [YourProjectName.Build.cs] and should be found in your project’s root source folder.
In this file, there should be a section called PublicDependencyModuleNames.AddRange(new string[] {}); in this you should add ‘SlateCore’ and ‘Slate’ based on what this thread is saying. Here is an example of what mine looks like, as a reference.
PublicDependencyModuleNames.AddRange(new string[] { "GameplayAbilities", "GameplayTags", "GameplayTasks", "Core", "CoreUObject", "Engine", "InputCore", "HeadMountedDisplay", "UMG", "Slate", "SlateCore", "AIModule"});
I hope this helps, and good luck 