in your devguide (https://www.jetbrains.com/resharper/devguide/Extensions/Deployment/LocalInstallation.html)
a paragraph tells: "In order to test the extension against a custom instance (or even the main instance), it needs to be installed, and needs to be packaged up in a custom
.nupkg file. This is detailed in the Packaging guide."
the link is broken: https://www.jetbrains.com/resharper/devguide/Extensions/Deployment.html
ps. This is a nightmare to test a plugin in a local instance. I'm sure you can do a simpler deployement way.