When extending the functionality of M3 panels in MForms you have three different options and these are JScript files, Script assemblies and MForms extensions. MForms extensions allow you to do similar things as with a regular JScript files but extensions are Smart Office features, written in a .NET language such as C#. The way extensions are deployed, configured and registered is also somewhat different compared to how you usually do with JScript.
This post is a brief introduction of how to create and deploy an MForms extension using the Smart Office SDK. Note that if you don’t have access to the SDK you will not be able follow along in the example on your own. I will also assume that you are familiar with the Smart Office SDK and will mainly focus on what is specific for MForms extensions.