Some of us (myself included) find that the dashed outline for the column bounding box when first added can be a bit difficult to readily see because of it’s light color and thin width.
This little bit of CSS will let you change it to suit your fancy.
Thanks to Christian Nelson for the suggestion.
.elementor-editor-active .elementor.elementor-edit-mode .elementor-first-add { border: 2px dashed red; }