Oh you're since in 1.4? Converting to 2.3 will likely cause some headaches. You may want to make something small in 2.3 before converting over to learn it's idiosyncrasies. I do think GMS2 is just a better program overall than GMS1 though. Good luck!
Yep, Zordak is currently made in 1.4.
I've made a game for a jam using GMS2 and I've got a side project up and running there as well so I know some differences at least.
That being said, porting it over will very likely not just be a one button thing.
Luckily I'm not using the room editor in 1.4 for example so there are no rooms in the project file, so things like that can be avoided at least, but still, will likely take quite some time to get it ported.
And it's not like I have much of a choice if I ever want to get the game up and running on consoles for example, but that's for the far future.
GMS2 on an engine level is definitely better but there's a lot of other things I really dislike about it. (workspaces...)
Anyway, this reply has become 500x longer than I intended so I'll end it here, thanks for the good luck. ^^