Character Panel Font Size Adjustment Using Mouse Click & Drag Not Working

I used to be able to adjust the font size of a text, or kerning, leading, etc. by hovering my mouse over the name of the function on the character panel. Two arrows would appear - one facing left, one facing right - and I could click and drag my mouse in either direction to either increase or decrease that particular feature that I wanted to adjust. Now, when I hover my mouse over any of these features, it stays as just my cursor. So I have to either type in the change I want to make, select from the drop down, or use the up/down arrows on the panel. The click and drag was so quick and convenient to use. I have no idea why this functionality disappeared one day or how to fix it. Does anyone know what I need to reset to get this feature back?