The small white thing on the bottom right

Your screenshot illustrates that you have enabled the iPadOS16 Stage Manager feature.

With Stage Manager enabled, you will see the new Windowed UI (User Interface) - and with this you will have different controls for the windows. The white “handle” that you describe is used to resize the related App window; while Stage Manager is active, you cannot hide these elements of the UI.

With Stage Manager disabled (arguably, this being the far more useful mode when using the iPad without a connected external monitor), you will see the established Full, Split and Slide-over views listed and accessible from the three-dot button. In this mode, you will not see the handles of which you complain.

Stage Manager can be disabled (or enabled) from iPad settings:

Settings > Home Screen & Multitasking > Stage Manager > Use Stage Manager on iPad - set to OFF

The Stage Manager feature can also be simply enabled/disabled from the iPad Control Centre.

benjamintheworld Said:

"The small white thing on the bottom right: When i try to open a new app, it makes a window. There’s a white thing in the bottom right and i want to get rid of it"

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Thank you or the screenshot.

Is this what you are referring to?*** If so, this is for changing the size of the window. It cannot be rid of, as it is built into the App.

***Screenshot