Apple - How do I trigger reachability in iPhone X?

iPhone X now supports Reachability

Just pull down on the bottom indicator to activate Reachability after turning it on. Also note that Reachability works with Control Center access so you don't have to reach that top of your phone to get to Control Center.

To turn on Reachability: Settings > General > Accessibility > Reachability

Source: Rene Ritchie's review.

You can't, the feature has been removed.

No “Reachability Mode” on #iPhoneX. The smaller casing and other optimizations make it easier to manage without.

Rene Ritchie on Twitter https://twitter.com/reneritchie/status/907734708397551616