Yes, I think this is what you want? Hold ‘Track Select’, then on the screen look for ‘Erase Track’ and select the track you wish to erase (A/B/C/D). That defaults/resets the sequence for the selected track.
Sorry that you seem to have some misgivings about the synth. Like many things I guess it’s just a personal preference, but I’d give it some time. I’ve owned and had opportunity to use a lot of hardware synths and the Pro 3 is among my favorites. I love the immediacy and how easy it is to setup modulations. As for build quality, I think it’s great? I wasn’t expecting all wood/metal for the price, everything feels solid and high quality. To me, plastic and wobbly knobs/sliders was just about everything in the late 90’s – this feels nothing like that. And above all… it just sounds amazing.
Hope you get along better with it or return it within your window to do so.