Review for Extra Folder Columns by Justuser
Rated 5 out of 5 stars
Confirm breaking of account names in smart folders (v0.4)
For GERMAN users - there is a patched version (thx to Colin Guthrie) for TB 3 with working account names at smart folders and german columns heading. Download here:
http://www.file-upload.net/download-2098433/extra_folder_columns-0.4-tbDE-patched.xpi.html
OTHER LANGUAGES: Edit column headers in "overlay.xul" to your own language.
Remark: Use at your own risk. It's a temporariliy workaround until this great 5 star extension will be updated again. I don't want to anger the author Joey Minta, there is no competetion.
To create your own collections, you must have a Mozilla Add-ons account.