As you have rightly mentioned, the new tab will also come with the sandbox environment properties, and some of the features will be restricted, similar to the app.
We do not have the flexibility to add these sandbox properties to the app by yourself or on our end.
I will record it as a feature request to add this feature to add this header to your app yourself or on-demand at our end. We cannot share any estimated timeline until the feature is picked up, worked on, and released.
I have used the browser’s window.open method to enable users in Freshdesk to click on a button on the ticket detail page (on the ticket_requester_info location) to open links in a new tab, if this works for you.
This would require you to use Javascript to trigger on e.g. click events however. Here is my example (using a Crayons <fw-button>):