edge [countable] the outside limit of an object, a surface or an area; the part furthest from the centre
I gripped the edge of my desk to steady myself.
the first spacecraft to travel to the edge of the solar system.
on the edge of something He stood on the edge of the cliff.
Stand the coin on its edge.
at the edge of something a big house on/at the edge of town
I sat down at the water's edge.
near the edge of something Don't put that glass so near the edge of the table.
She tore the page out roughly, leaving a ragged edge in the book.
the middle [singular] the part of something that is at an equal distance from all its edges or sides; a point or a period of time between the beginning and the end of something
in the middle a lake with an island in the middle
This chicken isn't cooked in the middle.
in the middle of something Her car was stuck in the middle of the road.
The phone rang in the middle of the night.
You can’t leave in the middle of the meeting!
His picture was right/bang (= exactly) in the middle of the front page.
I have a pain in the middle of my back.
Low temperatures in the middle of winter can kill some trees.
down the middle Take a sheet of paper and draw a line down the middle.
by the middle of something I should have finished by the middle of the week.
I like a story with a beginning, a middle and an end.
Normally, We say "Don't sit on the edge of the bed. Sit in the middle of it".
Now I want to change "sit" to "move".
Would I say "Don't move to the edge of the bed. Move to the middle of it" or "Don't move onto the edge of the bed. Move into the middle of it"?
Ngram shows the results of "move into the middle,move to the middle,move to the edge" but not "move onto the edge".