It is a pull out tray for some feature on your tablet MisterMarky. Precisely what feature I don't know so if you place your index finger on the curved button and draw it out by pulling your finger to the middle of your tablet whilst holding it on the button whatever it activates is what you need to go into your settings for and see if you can cancel it (you can use the search function bar in your settings if it is something not specifically listed in your settings). I had the same issue on my S21 Ultra with the draw out Samsung Pay tab or button at the bottom of my phone which I have now cancelled off my phone. Good luck to you and I hope this helps you.👍
