Not safe. Better way, to change a group icon, select the graphics source you want to use, copy it, open Tools > Show Info, select the icon for the target group, and paste the copied graphic. Work this way in Finder’s Get Info too, by the way.
So – say I have a folder of icons. I open the .png in Preview. Select all. Copy. Go to DEVONthink Show Info. Select the icon. Paste. In the image below: the file – the icon open and selected in Preview – the pasted icon in DEVONthink Show Info.
