It's **** easy with
CRU. Off the top of my head, you have to run CRU, ensure your monitor is selected in the top-left drop-down box, then click the top "edit" button and change the vertical refresh rate range from 30-90 to 57-144. Confirm that, exit the program, then run the restart64 program.
There are two minor annoyances though: you have to repeat the CRU process every time you install/upgrade your GPU driver, and the monitor will show an erroneous "FreeSync disabled because you're at 144 Hz" message every time you switch your refresh rate to 144 Hz (which should only be when you boot/wake your PC).