I followed simple Hello World sample from Create your first extension: Hello World example from the Microsoft Docs to build an extension for SSMS 2017
Created V
You got the first bit right, but there are a couple more steps to do before you’re set:
I explained this process in detail in an article I created at CodeProject. You can find the full tutorial at the following link: https://www.codeproject.com/Articles/1243356/Create-Your-Own-SQL-Server-Management-Studio-SSMS
First, you need to declare SSMS support in your source.extension.vsixmanifest file:
<Installation>
<InstallationTarget Id="ssms" Version="[14.0, 14.0]" />
</Installation>
Then I don't think VS can automatically install your extension for SSMS. So, run the .vsix file manually.