Is it possible to assign a keyboard shortcut to the arrow key?

Question

Do it yourself

It's rather awkward to click the down arrow (↓) to move to a new line. There is a convenient keyboard shortcut shift + enter, which creates a new line even if the cursor is not at the end of the line but in the middle of the text. I would like something similar specifically to go to the bottom (next) line under your own combination (for example, shift + space). I would be very grateful if someone could help me with this.