With the given tools it is sometimes hard to impossible to select a single stroke (which you might want to delete or change). Currently the selection box and lasso require the stroke to be entirely within the region. For drawing sketches there may be other strokes which are contained in this region, and those cannot be unselected.
I'd like to propose an inclusive version of the selection tools (box and lasso). One which selects any stroke that passes through the region. Checking if any of the vertices of a stroke lies within the regions may not be sufficient in some cases (long straightened lines), but would work as a first approximation.