Delete texts and attachments in Messages does not work on MAC as Described

I am trying to free up iCloud storage space - the bulk of which is in my messages which I like to keep synced to iCloud. I've made multiple attempts at reducing the size of the conversations by removing photos, but problem is you have to remove photos on ALL devices synced to iCloud, otherwise it still keeps them. On my iPhone and iPad I went through and deleted old photos and conversations were smaller, but on my Mac the photos are still there... so of course still being backed up to iCloud. So I followed the instructions in this article ( Delete texts and attachments in Messages in https://support.apple.com/en-us/HT204247) to free up space on my mac BUT when I select multiple photos/attachments within the message and select delete, it only deletes the first one I have selected. This means to remove all the photos I would have to select each individually, choose delete, confirm my delete and then move on to the next one. Anyone know a workaround? I tried going through finder to the area where messages are stored /my user name/Library/Messages/Attachments but then there are numerous numbered subfolders within subfolders within subfolders that contain the image and no easy way to tell which are associated with which conversation.