Custom registration string in FreePBX13 and PJSIP driver

Hi all,

In continuation to this topic, could you update me on whether custom registration strings in Asterisk 13 / FreePBX 13 and PJSIP channel driver are supported?

Parameter “Register string” is present in SIP trunk configuration, but I cannot find anywhere in PJSIP trunk configuration. Any ideas?

P.S. If it is not possible to define a custom registration string, how does its default format look like?