On the Layout Editor there is an option to "Change Icons" when in edit mode. This works differently to the "Edit Sensor Icon" on an individual sensor. It would be better and more consistent if they were the same.
The former works by clicking on the new icon then on the existing. The latter works via drag and drop.
Furthermore the former shows user icons under "files | icons ", the latter under "Preferences Directory | icons". Again it would be preferable to be consistent (if only for documentation reasons!)