You appear to have a Samsung Device.
Samsung Good Lock from the Galaxy Store has a plugin called “Navstar” using this you can customize the navigation bar & hide / show it at your leisure. You can also customize the buttons.
In my setup HERE you can see my home button is a different icon. I’m also utilizing “invisible buttons” for Recent apps, Back button & the additional buttons Navstar allows which let me skip & rewind any media playing.
Once you get this working please mark this as a solution. I don’t think the dev is looking to implement hiding the navigation bar as a new app feature as many android devices offer settings for it natively.