- Keep Ctrl down while dragging a line end: keep horizontal/vertical/45deg.
- Keep Alt down while dragging a line end: snap to the nearest snapping point within some distance, including endpoints of other lines and arcs (in the same layer).
- Keep Alt down while moving an object: snap, like above.
- Use grid which is coarse enough, draw lines so that each endpoint hits a grid point in the same grid. Drag a line end - a circular cursor is shown when two endpoints collide.
- Zoom in to make hitting endpoints easier if the grid/zoom level makes it difficult, i.e. if grid points are too close to each other in the view.
- Draw arcs with Ctrl down to create 45/90/180deg arcs.
- Generic advice: keep everything horizontal/vertical with Ctrl unless something else is really needed.
- EDIT: “Limit graphic lines to H, V and 45 degrees” in pcbnew preferences limits the angles automatically and reverses the function of Ctrl while drawing a new line. However, it doesn’t affect editing existing lines.
- Select an item, go on top of a small square endpoint (including arc endpoints and center point) and press M to start moving, grabbing from that specific point.
These work for 5.1.5. It’s very, very easy to create horizontal/vertical edges this way, also fillets with 90deg arcs. Adding other than 90 or 45 degree corners may make it a bit more difficult or much more difficult depending on the case, at least if you have to add fillets or calculate some dimensions.
Alt is somewhat problematic on Windows which tries to steal it for opening menus - you may need an extra click or Esc in some situations.