Are these all OK?
to the top right corner of the screen / to the upper right corner of the screen
on the bottom right corner of the screen
at the bottom right corner of the page

Question

Answer

The places are fine. The only thing I would look at is the preposition:

'In' we use for something actually part of the computer. The icon is in the bottom corner
'On' we use for something on the screen a mark or dust for example
'To' we would use to direct a movement. Move the cursor to the bottom of the screen for example.

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