@joshijay655,
If you set in layout['yaxis'] the range=[c, d], then a vertical line through a point of coordinates (a,b) is defined as a scatter plot with mode='lines' and
x=[a, a],
y=[c ,d]
@joshijay655,
If you set in layout['yaxis'] the range=[c, d], then a vertical line through a point of coordinates (a,b) is defined as a scatter plot with mode='lines' and
x=[a, a],
y=[c ,d]