While I have hotkeys set up to allow me to scroll or press keyboard inputs to scrub through frames, or drag the playhead, is there a way to set up viewport scrubbing? Something like holding a hotkey and move the mouse left or right?
I generally use the hotkeys. Hold right or left arrow key down. If you want to scrub between keyframes instead of each frame then use up and down arrow keys. By default spacebar plays animation between the start and end keyframes. You can switch to preview start and end frames by clicking clock icon on timeline editor's header. This lets you set a different start and end frames from the scenes start and end.
***Edit***
Note: if you press spacebar to start playing and hit esc key it goes back to the frame you were on when you hit the spacebar. Where as if you hit spacebar a second time it stops on the frame you hit the spacebar in.