Me – I thought the expression would have been ‘Waiting Staff’- but what do I know? Even as I type, Word suggests I split into ‘wait staff’.
Collins Dictionary does not like ‘waiting staff’ but has ‘waitstaff’ as a North American English word - (US & Canadian) the collective term for waiters and waitresses – Cork’s northside not being a hotbed of American English may be my excuse. But I know now.
Chambers does not recognise ‘waitstaff’ or ‘waiting staff’.
I knew what was intended by the sign as I suspect did all readers so it is probably another case of “Words are in dictionaries because they exist – they do not exist because they are in dictionaries”