VLAN membership is not an information retrieved automatically by NPM. You will either need to use a UnDP or populate the information manually in a Custom interface property.
Concerning the resource itself, you need to know a bit of ASP before to edit it.
The resource you are talking about is located there:
Note that every change you do will be overwritten if you run the configuration wizard.
Customization of the Web Console is not supported, so if for some reasons your view is messed up, the support team will not help you.
However I am sure you will get support from other thwack members to manage to get this done.
If you do not want mess with the ASP files, simply submit your idea in the Feature Request section: