Hello,
Greetings from the Freshworks Community!
Currently, the only option to auto-populate the field value is with the help of workflow automations. You can configure a workflow for each of the country and update the respective country code fields.
PFA sample workflow setup:

However, this wouldn’t be a feasible solution as individual workflows will have to be configured for each country value, which will consume the workflow limit of the account.
Therefore, currently, there is no direct option to auto-populate the field value but only to provide the choices to choose from them manually.
I hope this clarifies. Do let us know in case of any further queries, we’ll be happy to help out.
Have a great day!
I have asked for this as well - it’s functionality I used to code in desktop apps 20 years ago, so perhaps it’s not possible in browser apps, except the Status and Priority system fields do have default values 😏. Only answer seems to be a custom app. Ticket creation automation is too late - I need to show the user a field with a dropdown defaulted to a value that will be correct for 80% of users, so I don’t want to have to make that 80% always select from a dropdown