Exported settings from FF59, checked ok for content in the exported json, and run import on FF 58/60, each with a maiden profile and no other extensions installed.
Each import attempt removed the preset https://*.googlevideo.com but otherwise the fields are just blank.
Whilst I personally would prefer #8 the import/export is a good alternative, if working though
WIN 10 _x64 1709 16299.125 FF _x64 v 58.0.2 / 59.0b7 / 60.0a1 (2018-02-08)
Exported settings from FF59, checked ok for content in the exported json, and run import on FF 58/60, each with a maiden profile and no other extensions installed. Each import attempt removed the preset
https://*.googlevideo.combut otherwise the fields are just blank.Whilst I personally would prefer #8 the import/export is a good alternative, if working though