Pressing Ctrl + Space on Windows or Command + Space on the Mac will change the cursor to a magnifying glass. Dragging the canvas while in magnifying glass mode will enable you to zoom in and zoom out on the canvas screen.
How do I select multiple areas in Medibang?
If you already have a selection range, you can add a selection by holding down the Shift key and creating a selection range. Hold down the Ctrl key and cut the selection.