Hover button

If you really need to achieve this, you could work around it with JavaScript by temporarily raising the caption’s position using z-index when the button is hovered, then restoring the original z-index once the button returns to its normal state (attached).

That said, there are many reasons why this approach may create more problems than benefits, as JudyNollet​  and PhilMayor​  pointed out in their comments, and their reasoning makes perfect sense. If you are not comfortable with JavaScript, or you are not familiar with modifying code, working with z-index, and managing element stacking behavior, I would not recommend this solution. In that case, it would be much better to place each caption on separate layers, as suggested by Phil and Judy.