As long as your project’s Target.cs has LinkType = TargetLinkType.Modular, all you need to do is compile the solution in visual studio with Shipping configuration.
It will rebuild engine source and project if necessary (if not already built or if modified), but after first build it will only rebuild parts you have modified (ie. the plugin).
It should produce a DLL in the plugin folder
Plugins/YourPlugin/Binaries/Win64/UE4-YourPlugin-Win64-Shipping.dll
I am not familiar with plugins including content, but I expect it should work the same, with plugin’s cooked content ending up in
Saved/Cooked/WindowsNoEditor/YourPlugin/...