We use Freshdesk to support multiple products. Since products have different characteristics, we have created ticket fields that correspond to a particular product (but are not relevant for others). Freshdesk exposes ticket fields (default and custom) to both agents and requesters (portal) for ALL products. There needs to be a configuration option through the UI to associate fields to 1 or more products.
There are numerous posts on the Freshdesk discussions requesting this feature. It is difficult to correlate all of them since some people refer to this as ticket forms, but I assure you this is a necessary feature. I myself have opened tickets with support years ago and requested my issue be converted to a feature request.
The responses I have received and seen on the portal suggest 2 solutions (both of which are unacceptable)

