1. NORMAL WAY:
Aim and click on a belt snap point. Aim and click at a different snap point within range and height limit. Aim, click, aim, click.
2. SUGGESTED ADDITIONAL OPTION:
Requirement: Two snap points within range and at equal height.
While holding SNAP, aim and click on a belt snap point. A full belt will be built between the two points. Aim, click.
Like any other belt building, before you click to confirm, an indicator is shown for the resulting belt and its direction.
Optional: To change belt direction, use mouse wheel or start at the other snap point.
Optional: Belt instead snaps to (nearest) lowest valid snap point ahead in a straight line. Use scroll wheel to switch to higher snap points if available. To change belt direction, start at the other snap point.
Easier belt building. Save time and effort when building long straight belts. Building a large central bus or a set of belts over a long distance is currently very tedious.