I could not get any of the samples working to where I could step through the code for debugging purposes.
But I did find an old project of mine. It did not seem like it was doing anything but then I added some printf lines to it to see when it is loading and when the event is triggered. So I do have this extension manager loading now but I am having an issue with it logically for what it was originally designed for. So I am working on changing that.
If the dll and pdb file is in the Domino directory and you have a break point in the code you can attach to nserver and when it hits that breakpoint it will stop there and allow you to step through.
When I am done getting everything working like I want I will come back and create a webex recorded video how to take simple sample I have, put in projects folder, how to configure project settings, compile to DLL, and then how to step through the code to see it working. When done I add to youtube and then add link here. Hopefully it will save someone time in the future.