You can have your own custom Pre/Post build events to be triggered when a build is finished. Only applicable for C++ projects.

Open your uproject file in notepad (or any text editor) and add the below key.

"PostBuildSteps": {
             "Win64": [ <Example: Run a bat file.> ]
}

For example, below uproject file will run CopyDLL.bat file.

{
     "FileVersion": 3,
     "EngineAssociation": "",
     "Category": "",
     "Description": "",
     "Modules": [
         {
             "Name": "YourProjectName",
             "Type": "Runtime",
             "LoadingPhase": "Default"
         }
     ],
     "PostBuildSteps":
         {
             "Win64": [
                 "call \"G:\\UnrealProjects\\MyProject\\CopyDLL.bat\""
             ]
         }
 }