In OneNote for Windows 10, you can quickly select all nearby ink strokes without having to manually draw a selection around all of them.
Do the following:
Open the page that contains a drawing whose ink strokes you want to select.
Tip: To create a new drawing, see Write notes and draw in OneNote.
Double-click or double-tap any ink stroke on the page.
Doing so will select the ink stroke, as well as any additional ink strokes that are near it on the same page.