On Transifex i see this string: Show '_Open _Folder' I guess it should only have one "_".
I also think there is an extra underscore here. According to another similar string (Show 'Open in _Terminal' ), I guess the correct string should be: Show 'Open _Folder'
Andre Miranda referenced this bugreport in commit 7f530d0d50bed2f4d468b219ecb53d999828b0d4 Remove extra underscore (Bug #16266) https://git.xfce.org/xfce/xfce4-panel/commit?id=7f530d0d50bed2f4d468b219ecb53d999828b0d4