Hi and welcome to the forums.
I don't know the exact specifics for the NESMaker engine but technically speaking it should be possible. The main problem I'd guess would be modifying the code so to be able to turn gravity on and off. I am generalizing of course. You could ask the 8bit Hero guys at the facebook group.
A few notes to get you started:
+ Read about this important fix for 4.0.11:
http://nesmakers.com/viewtopic.php?f=27&t=735
+ Currently the search field on the forums is broken, so if you experience trouble use your favorite search engine using a query similar to this:
my question site:nesmakers.com
+ Tired of pressing a key to get rid of the output command line window every time you export to test?
Then take a look at this post.
+ Delay the music part for last after riding the initial NESMaker learning curve.
Read this thread for information on some technical quirks regarding music in NESMaker.
+ If you need flasher drivers unfortunately it's a bit confusing how to go about it. If you got the new mini flasher (looks like the
photo in this post) then you need to ask Infinite NES Lives for the drivers. You can do this by opening a support ticket at the INL website. If you got and older flasher with the bigger board (
similar to this one --- may not have all the slots as the one in the picture) then the drivers are located under "Flasher" inside your NESMaker install folder.
+ You can ask questions here, on
the facebook public group or at the
Community Discord server.
Good luck!