Annoying trace lines on Samsung Tab A screen

On our new Samsung Tab A which I have just bought for my wife something has switched on a feature which draws dotted trace lines on the screen, which disappear shortly afterwards (just as well). Also there is a coordinates bar at the top of the screen. I have been trying to turn the feature off, it is just annoying. What is more annoying, I cannot find how to turn it off. I have searched Settings over and over, plus the pdf manual, which is useless as usual.

Can someone tell me how to get...

Annoying trace lines on Samsung Tab A screen

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