I have a closed project which I have installed from a third-party who have given us access to user and approve if it works for our requirements. One of the Views they have built is extendable. I reached out to they're support desk to ask how I can extend it and they advised "using general Umbraco techniques" I'm not sure what that means so asked for a demo or sample code which they can't provide as their lead developer is off sick. Does anyone know the general Umbraco techniques for me to obtain this View and add to it using C# or whatever is possible?

It is a bit of an open ended question though.. perhaps you could be more specific? One thought could be if it's package based..... If it's a RCL (razor class library) based package then you can override the view by putting a file at the same physical filepath location... Like Umbraco Forms.. however to help with this UmbracoForms gives you a download to access the default view implementation. https://docs.umbraco.com/umbraco-forms/developer/themes Though if the package developer hasn't provided the source for the default views.. then you might have to go decompiling dll's to find the

AspNetCoreGeneratedDocument

though even then it's not all that easy to reverse engineer back to a cshtml file? Other's might have insight here.... But hopefully you do simply have a physical View (template) that you can manipulate.. though saying that if it's marked immutable by the package developer then any changes you make will be reverted on build (as nuget restores them back to the package developers intended state) So then you'll have to have your own buildtarget that copies your duplicated external file back in, if you want to leverage MSBuild.. or a script in your deploy process to do the same..