New a project, new a graph window, double click Y axis to open dialog.
Go to Reference line tab, type for example 5 in the At Axis Value grid cell, click Apply button.
Go to Breaks tab, activate Horizontal panel, set Number of Breaks as 1.
Set Break From as 0 (scale’s from), Break To as 10 (scale’s to), click Apply.
==> The Reference line disappeared.