Control the size of an icon inside a button or hotspot

Need full control over the size of an icon inside a button(except S/M/L). You can only control the size of the button/padding arround it.

Need full control over size of button. S/M/L is not enough.

Need full customisation of buttons via import of SVGs, not just the icon inside the button. (This can be achieved by inserting an SVG and making it interactive but being able to create and save new buttons would be much better UX.)