Hey, there should definitely be no issues using a marketplace plugin with a source build, I’ve done that often.
Just install the plugin on a binary version of the engine first and then *migrate *it out from there to your own project’s plugin directory or your custom engine build.
So move the plugin from <YourBinaryEngineInstall>\Engine\Plugins\Marketplace to <YourProject>\Plugins or <YourCustomBuild>\Engine\Plugins\Marketplace (haven’t tested the latter case, because I usually put mine with the project)
After that you may need to open your project’s Build.cs file (“YourProject.Build.cs” ) and add the “DonAINavigation” module as a public dependency.