What problem does this address?

Currently with the button block, I can choose several popular widths, 25%, 50%, 75%, 100%. However I want to create a pattern with 3 buttons together in a row, and need to provide a more specific pattern. Example of the pattern:

What is your proposed solution?

Keep the popular widths, but have an advanced option to provide a specifics widths, px, %, rem, etc.