Many thanks, jgb. Don't suppose you can help with the 'filleting' question? 😲

@jgb said:

spogadog asked: Also, how do you DE-select unwanted lines/faces from an area you have clicked and dragged out for, say, re-scaling?

Use the Select pointer/tool but hold both SHIFT and CTRL keys down as you click on unwanted lines or objects. Using only CTRL adds items to selection set, just SHIFT toggles items in selection set.