You don't have to do that with Syncthing. See https://docs.syncthing.net/users/introducer.html
> The introducer feature lets a device automatically add new devices. When two devices connect they exchange a list of mutually shared folders and the devices connected to those shares. In the following example:
> Local device L sets remote device R as an introducer. They share the folder “Pictures.” Device R is also sharing the folder with A and B, but L only shares with R.
> Once L and R connect, L will add A and B automatically, as if R “introduced” A and B to L.
> Remote device R also shares “Videos” with device C, but not with our local L. Device C will not be added to L as it is not connected to any folders that L and R share.
