How to set Gutenberg preferences programmatically with wp.data.dispatch?

Question

This correctly shows true/false when the option for Reduce the interface is enabled/disabled through the GUI.

Are you sure isFeatureActive( 'reduceInterface' ) worked?

Because I looked at the source code (see wp-includes/js/dist/edit-post.js) and then I found out that the feature name is actually reducedUI and not reduceInterface.

So try with reducedUI instead:

let reduceInterface = wp.data.select( 'core/edit-post' ).isFeatureActive( 'reducedUI' );
console.log( 'before', reduceInterface );

wp.data.dispatch( 'core/edit-post' ).toggleFeature( 'reducedUI' ); // enable/disable it

reduceInterface = wp.data.select( 'core/edit-post' ).isFeatureActive( 'reducedUI' );

console.log( 'after', reduceInterface );

The above worked for me on WordPress 5.8 and 5.8.2 (the latest release as of writing).