Hi @KrissKdash,
I believe you're hitting a limit on the number of Y items displayed not because of an actual upper limit (that then must be modified via jsl, etc), but because the text would overlap given the size of your graph, and so Graph Builder is hiding those labels to maintain legibility. You could try making the font size smaller for your Y axis in the Axis Settings, then Font, which should allow you to display more items. Alternatively, try making your graph larger vertically. You can even make it larger than the window side by turning Fit To Window off in the top red triangle > Fit To Window > Off. Then, resize the graph by dragging the corner of the graph, not the window.
As for resetting the axis, a helpful option to know is Revert Axis, which you access by right-clicking any Axis (JMP-wide), then select Revert Axis, which will reset the axis to the original settings.
I hope these help!
@julian