Use the View Panel
The View Panel is a vertical group of four controls in the lower-left corner of the Argumentation.io workspace. Select the controls with a mouse, or use Tab and Shift+Tab to move keyboard focus to and through them.

Zoom in
Select the first control, marked with a plus sign, to make the map appear larger.
Zoom out
Select the second control, marked with a minus sign, to make the map appear smaller.
Fit the map to the available space
Select the third control to adjust the map’s scale and position so that the complete map fits within the available canvas area.
Show or hide the mini-map
Select the fourth control to show a miniature overview of the map in the lower-right corner of the workspace. Select the control again to hide the mini-map.
The mini-map is particularly useful when the complete argument extends beyond the visible canvas.