Customizable heatbed knob

If you are not satisfied with the sizes of the adjustment knobs you find in Thingiverse, here you can customize one to your liking....

You can choose diameter of the knob, if you like spikes, how many and what size...just as you draw it...

It will leave a void for the nut so you should insert before the printer add the top layer of the nut "cave", or if your printer can bridge it just do it after printing.
The radiuses of the for the nut's cave are listed here, then consider your printer'