Can you add methanes ?

[ToumanLin]

Will you add methanes ?Which is used in "Cryogenic Engines (it is belonged to "near future series")"
I found the mod supported NF propulsion, so it is sorry that there's no methane in the editer.
SO, will you add it ? Or can you tell me how to add it ?
(My English is poor, Hopefully that above makes sense to you )