Note on the viewer, if you double-click the ligand, it zooms in. I haven't found a way to zoom in general. The "Toggle Expanded Viewport" option, the fourth icon from the top on the right, gives a larger view.
(Edit: maybe the double click is a triple click or a double-double click, but anyway, if you click enough, it will zoom in on the ligand.)
Use the mouse wheel Loci, rolling forward moves it closer, rolling it towards you moves it further away.
Yes, the mouse wheel does it. I also found something about "drag using three fingers" to focus. I think that's maybe where the triple click comes in, no actual touch screen here. That's under "Settings/Control Info", fifth icon from the top right. Then there's a "Moving in 3D" section.