Copying and applying a crop to images

Select the image that you want to copy the adjustment from in the browser. The thumbnail will have a thick white border then.
Now select the image thumbnails that you want to apply the adjustment to. The thumbnail(s) will have a thin white border in the browser.
Make sure the Edit All Selected Variants is selected in the toolbar or from the Image menu.
Press the small double-ended arrow icon. A dialog box will appear.
Press Apply at the bottom of the dialog box. The adjustment will be applied to the selected images.