Can't delete a photo attachment
When composing an email on iMac Mojave Apple mail with a photo... before sending.... and then deciding I want to delete the photo and wanting to add a different photo, I cannot delete the photo. When I go to.... Message>Remove Attachment... it is greyed out so I have to completely close out the existing email and recompose a new one with a different photo. Seems by clicking on the photo, I should be able to click on 'Remove Attachment' and that should delete it but 'Remove Attachment' is not operational. Does anyone now of another way..... or do I have to always recompose a new email each time I want to change my photo? Somewhere I read something about something might need attention in the Library but I have no idea how or what to do that regard. Can't imagine why 'Remove Attachment' would be greyed out. Thanks for any help anyone can provide.
iMac 21.5″, macOS 10.13