How to set up 2 Fitbit devices to same account?

[SunsetRunner]

In the past I was able to set up an older and a newer Fitbit device on the same account. Sometimes I wear the old one and other times I wear the new one. I bought a new Charge 5 and in order to set up the device on my iphone, I have to delete my old Inspire 2. I called customer support and was told I cannot set up both devices to the same account. I find that disappointing and unsatisfactory. Does anyone know of a way to set up 2 devices to the same account?

[JohnnyRow]

The key, as you said, is an older and a newer device, older being much older, like probably few still in existence.

From Can I use more than one Fitbit device with the same account?