My bad, I guess that isn't an option in AMD 5000 series.
On to undervolting! THIS IS A SAMPLE SCREEN FROM AMD, NOT NECESSARILY FROM A RX5700
Best just to enter the new voltage values numerically in the boxes. Try subtracting 50 from each of your stock voltage values and test stability (and clock speed)
You can also enable "Power Tuning" (right side of screen above) and increase the power limit above 100%. Increasing the power limit does just that, it allows the GPU to pull >100% of the stock power limit. It's better
to undervolt first (which reduces power draw, hence heat and noise also). If the stock limit is 180W and you're hitting that limit before the frequency hits max, undervolting will reduce power draw and allow the max frequency to be reached at/under 180W power draw. Increasing the power limit means the max frequency will be reached at >180W power draw.