When customize controls activated, there's an issue regarding scaffolding, that is, the jump button becomes small after using scaffolding (see the first attached video). This can be annoying and dangerous while encountering emergency.

There is an issue regarding swimming as well. When swimming, the size of the buttons that are used to control up and down become smaller compared to that of the jump button. (See the second attached video) (Don't know if it's customize controls only)

Neither am I sure that if they are really bugs nor just features, either way, they could bring inconveniences to us. If these can be fixed or improved, I think we can have a better experience with the Minecraft world. 

I appreciate your time helping me with these issues,

Best regards.