Hi Barry, that's what "Straight Snap" on the bottom toolbar is for. If straight snap is enabled, then when you move if you keep your mouse near the x axis direction it will snap onto it and you'll see a dashed line going in that direction with an axis letter label at the base point.

You can also hold down the Shift key to force straight snap to engage to the closest axis line no matter how far away you are from it.

If you're having difficulty with keeping the regular straight snap engaged though it's probably due to your high screen density. Try increasing the values under Options > Snaps > "Straight snap options" for "Activate distance" and "Keep active distance".

The "Activate distance" is how many pixels you need to be away from the actual axis line for straight snap to engage, and the "Keep active distance" is how many pixels you can be away from it to keep it on after it has started.

- Michael