There are several purposes imaginable, where you need to “stack” some diagrams among themselves to be able to see the exact situation in different diagrams at the same x position (time, for example), like it is in stocks analysis.
Currently I can’t position the y-axis at an exactly defined location, which makes it impossible to align diagrams to each other.
You say you can’t position the axis at a defined location. What have you tried exactly to attempt that?
I use “Format the axis” to adjust the scale and end-points of the axes on my charts. Double-click on the chart to put it in Edit mode. Left-click on the axis to be adjusted, then right-click on it to bring up the dialog box. Choose “Format the axis”. There are tabs for scale, numbers, font, etc. Many adjustments can be made. HTH.