If your downloaded on-screen buttons aren't appearing or keep disappearing, check your system's battery optimization settings. Android often "kills" background apps to save power. To fix this, go to Settings > Battery > Optimization and select "Don't Optimize" for your navigation app.
Long-Press Actions: Assign different tasks to a long-press, such as opening the camera or taking a screenshot. download on screen navigation buttons
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Accessibility: Larger touch targets for users with motor difficulties. How to Download and Enable Navigation Buttons If your downloaded on-screen buttons aren't appearing or