Curve tables are supported primarily for 2 purposes
Expose Live Config data to GameplayEffect
Gameplay Effects use FScalableFloat to provide data. While it is possible to provide live config data as set by caller values, this can be inconvenient.
Import existing data
If your project currently uses curve tables, you can easily import that data into the live config. This will tag that data as coming from a curve table.
How-to
In project settings, specify a curve table to export properties to, and/or curve tables to import properties from: 
Properties that are exported or imported will be updated automatically. When live config data is changed, it will be updated in the export curve table.
TODO: Turn import tables into a single action rather than a property