Mouse gestures are easier to customize in 2018. (Below 2017 customize menu).
You can set the number of mouse gestures to 2, 3, 4, 8, or 12 gestures. If you set the number to 2 gestures, you can orient them vertically or horizontally.
To set the number of mouse gestures, click Tools> Customize> Mouse Gestures. From the drop-downlist, select the desired number of mouse gestures.
You can also customize the mouse gesture assignments through a visual drag-and-drop user interface.
Drag tools from the list of commands to any of the mouse gestures guides. If you drag a tool to an empty position, the tool is added to the gesture guide.
If you drag a tool to an occupied position, it replaces the tool on the gesture guide.
If you Ctrl+ drag a tool from one gesture guide position to another, it is copied to the second position. You can copy a tool within one gesture guide, as well as across gesture guides.