Bulk edit Metadata
Bulk edit metadata in modern document libraries
This is already possible using the Edit Properties function. Select the files you want to bulk update and click Edit Properties. Changes applied there will update all the files selected.
Miriam Stark commented
I would like the Bulk Edit Metadata to allow appending rather than overwriting.
Jordie Wolf commented
@Erik it is already possible, but from my experience this quick edit will not update more than two files through this quick edit. I must say that I've only tried updating files with one column with a managed metadata list.
Isn't that already possible through QuickEdit?