I was wondering if it was possible to customise the admin views for Merchello?

I want to store custom information for a sale, and it would be better to have it in a custom field, rather than as a note or a line item. Is it possible to add new / override existing views?

If so, can someone explain how I'd go about this please? I've spotted

<tree id="sales" title="Sales" icon="icon-receipt-dollar" routePath="merchello/merchello/saleslist/manage" visible="true" sortOrder="2">

but I'm not sure how I'd go about implementing something myself, or what I would override.

Thanks.