You can only configure Jami to use one bootstrap server, one DHT proxy, one TURN server and one STUN server at a time. Please allow for multiple servers to be added at once for a more robust, decentralized configuration.
This way one can be connected to several servers of any kind.
I was not aware bootstraps and dhtproxies can have multiple entries. I would suggest making the UI more clear on allowing for multiple boostraps and dhtproxies
For the use case of multiple TURN servers, if some of your friends use a different TURN server than the one provided by Jami, you can still be connected to every one of your contacts without having to switch between TURN servers manually. It also helps make Jami with the TURN server connections more distributed and not centralized.