Twine is so much easier to use because I can see where the answers branch off and I don’t have to do as much of my own coding. Is it possible to export a Twine file and adapt it to submit as a game?
Example
*commend
Indent
It wouldn’t be as simple as just making a few tweaks to an existing document. You would have to learn at least the basics of writing ChoiceScript code, since it’s an actual programming language, not a tool like Twine where it’s possible to create a simple game without writing any code at all. There are some pretty significant differences in syntax in ChoiceScript, so any code you have written will have to be altered to conform to those, and you’ll have to learn the commands that actually drive the game forward, which I think Twine does by using brackets to link things.
None of this is meant to discourage you. If you’ve already done some coding, you’ll probably pick up ChoiceScript pretty easily. If the actual plotting and writing of your game are finished, so that you’re just focused on the mechanical aspect of rewriting it in ChoiceScript, I suspect it will go quite quickly once you get the hang of it. How much work is actually involved will depend largely on how complex your game is. If the story mostly works by branching text, that will be easy to rework once you learn a couple of basic ChoiceScript commands, but if there are a lot of variables involved (especially if your game is stats-driven), it’s going to be trickier. (And of course, all of this assumes that your game doesn’t have anything essential in it that Twine can do but ChoiceScript can’t.)
As someone whose made games in both, you’d need a fairly major rewrite. They’re different languages, not interchangeable in code or interface.
COG only accepts choicescript games. Nothing to stop you putting your twine games in another platform like itch though if you want to continue to use twine.
Depending on how you have structured your game and choices, OP, it might however not be that tricky to convert/rewrite from twine to choicescript.
I agree to a point, but there’s reasons why most of the games slated for conversion into twine years ago never made it and the annoyance of recoding then into a completely different system is one of them. It is possible to swap out at least sone of the basic variables if they’ve just used the basic templates and code, but gets progressively tricker to get right the more complicated and longer a game gets.
Even a basic conversion, while very doable, is still a decent recode to get working properly. Definitely possible, but unless it’s a project I’m really fond of or still very early in development, I’d be inclined to publish the existing one in twine and start a new game in CS from scratch, but that’s just my take. OP is welcome to give it a shot if they want to 
Twine is not a programming language. It’s both a framework and a developing software. Twine Story Formats (I hate that name, it just complicates for the sake of it) are the actual programming languages, and there are a few of them: Sugarcube, Harlowe, Snowman, Chapbook, etc. The only requirement to be considered a Twine language (sToRy FoRmAt 
) is to use passages and links, and this is the only resemblance between them.
ChoiceScript has a limited feature set, so they’re easy to replicate in any of Twine languages. The reverse is not true at all.
However, if all you want is to take advantage of Twine’s UI to visualize the branching of your story, I would recommend using Snowman (it’s the most barebones, no bells or whistles, of the bunch) and write using ChoiceScript inside each passage.
This is not going to make the game functional – you won’t be able to properly play test --, but you could later export as twee files and make small adjustments, replacing headings with label commands and links with choice commands. This requires that you be very mindful of the syntax of both languages.
There were previous attempts in the community to create transpilers (bridge converters). I’m not aware if any was successful.
I’m not sure if I understood the question, but you can’t submit the same ChoiceScript game in a competing game format (Twine), but you can with submit sequels, prequels, or companion material.
Creating a system that can covert Twine to CS or learning CS is your best bet for now.