When You build your plugin you will find build version of your plugin inside "Nop.Web\Plugins".
So you should find your cshtml in "Nop.Web\Plugins\Chat.MainChatPlugin\Views\Configure.cshtml".
Copy version of other plugins _ViewImports.cshtml should work just fine.
if you can't find your cshtml file inside "Nop.Web\Plugins" folder then you might want to look at your plugins csproj file.
You can take help from other plugins csproj file or check other plugin Notes.txt.