Office 365 - drag message to folder
In Office 365 - Outlook: - Drag an e-mail message from the inbox and drop it into a folder Nothing happens in Vivaldi. In other browsers, such as Firefox or Google Chrome, the message is indeed moved to the folder. Alternative - non-preferred - way to achieve a 'move to folder' in Vivaldi, is to go via the RMB click menu.
I just discovered that this old problem has been fixed in 1.7.725.3
(or perhaps a few two builds earlier ;-) )