We used to have a multi-ending feature, but it was so under-utilised that it got dropped when the site was redesigned. No idea what happened to the few stories that did use it.
Depending how long the story is, you could maybe split it at the branch point. And at the cliffhanger ending of the main part, offer a "choose your own adventure" style option:
If you think Peter should jump into the ravine, read "My Killer Story - Alternate Ending 1"
If you think Peter should run back to the main road, read "My Killer Story - Alternate Ending 2"
...
Then, submit each ending in quick succession and link them as a series so they're collected together and clearly signposted in the title that they're alternate endings. Or seek a willing mod who will allow you to submit all the parts at once so they can all be locked and approved in one sitting.
In the Author Note of each ending, clarify this further by informing people that it's a continuation of the main part and they should read that first, just in case someone lands on the ending directly from a search engine.
The difficulty here would be that the individual endings are all "chapter 2" of the same story and must therefore abide by the rules of being a decent enough length (ideally 1k+ words) on their own merit. If your endings are all really short, that wouldn't work.