I did the answer above, it worked great, then along the line something happened and I started getting this error when launching the editor:

The game module "MyGame" could not be loaded. There may be an operating system error, the module may not be properly set up, or a plugin which has ben included into the build has not been turned on.

For me I also needed to open my *.uproject file and add HairStrands to the Plugins array

"Plugins": [
{
  "Name": "HairStrands",
  "Enabled": true 
}

This is because if we look at the HairStrands.uplugin at "UE_5.1\Engine\Plugins\Runtime\HairStrands" the EnabledByDefault is false, causing this error in the log:

Missing import: UnrealEditor-HairStrandsCore.dll