In Motion Explorer, select a recording which contains the ROI you want to copy. Right click on the Recording Name to reveal the "Copy ROIs" option in the pop-up menu.
Or, select the Recording Name and them select the "Copy ROIs" icon from the top ribbon toolbar.
Select the Recording Name that you want to paste the ROIs into and right click to reveal the pop-up menu.
You can also use the Paste ROIs icon from the ribbon toolbar.