Is it possible to set the position and size of the modal form and dialog boxes?
Looking at https://developers.freshdesk.com/v2/docs/interface-api/ there is no reference to being able to define the position or size of modal forms.
Or do developers have to abandon using the interface API and develop their own solution based on iframes?
I see you also raised this question as a support ticket, which must be because you did not see a response here for a while. Apologies for that.
As we responded in the ticket, there is currently no way to set the position or width of the modal. This is restricted by design by the Freshdesk product, and the current modal is what is available to app developers.
We do recommend trying to use this wherever possible, but do understand where you might want to go beyond the available feature to accommodate your requirements. I have shared this feedback with the product managers in Freshdesk and they should be looking at this.