You need to download the latest version of NavStar, which isn't available in the Galaxy Store.
First, uninstall the NavStar module in Good Lock.
Next, head over to ApkMirror and search for NavStar and download the latest version 6.1.05.40 or use this link to go straight there
https://www.apkmirror.com/apk/samsung-electronics-co-ltd/samsung-navstar/samsung-navstar-6-1-05-40-r...Once downloaded, head back to Good Lock and open NavStar. The 'enable extra gesture settings'will now be there. Enable this and head straight to Settings, Display, Navigation Bar, More Options, then the option to hide the Gesture Hint will be there. Enable this to hide it.
The Galaxy Store doesn't have the latest version of NavStar at the moment, hence why this option wasn't there when you checked.