Hi,
When the hovermode is set to 'x' and the hoversubplots='axis' option is used, the x label can be hidden by the labels of other subplots. This issue can also be found in the plotly python documentation, as shown below:
In this CodePen, the problem arise when hovering the first point of the first subplot or the last point on the middle subplot.

I believe it would make more sense to stick the x label at the bottom subplot, regardless of which subplot is hovered over, especially when the spike line is enabled. I implemented this, and here is what it looks like in my use case:

Please let me know what you think.

Thanks!