Glad to hear that you’ve been elevated!
Couple of clarifying questions:
When you say ‘old developer portal’, do you mean apps.twitter.com?
If so, all of your owned Twitter apps on apps.twitter.com should directly translate to the new app management dashboard on the new developer portal on developer.twitter.com. You should be able to see all of your old Twitter apps created on apps.twitter.com alongside any of your new apps created on developer.twitter.com in the new app management dashboard. All of your authorized users will be attached to your apps, regardless of which dashboard you are managing your apps through.
Knowing this, can you continue to use your old Twitter app to manage your integration with Twitter dev products and your production app?
If you would still like to transfer over to a new Twitter app, you will have to have all of your users re-authorize that app. I’d be curious as to why you’d like to do this as well.