As Kids, we were taught to say Good Morning/Good Afternoon /Good Evening by way of greeting (depending on the time of day of course…)
and when we left… we would say Goodbye /Goodnight
(and "thank you very much, please may we come and visit again " as applicable. ) 
Goodbye… to all who left .as they left… was sufficient,
unless they had brought goodies and we wanted to encourage them to visit again
in which case we thanked them for whatever and smiled appealingly/appallingly
We don’t really say anything on a day to day basis but the op asked what the equivalent was, perhaps the real answer is nothing or there isn’t one but that’s the translation I would use as ‘good appetite’ would never be said in English.
Same at my school, we changed the words to ‘for what the pigs have just refused may the lord make us truly unthankful’!
When my eldest was a baby I had a friend with twins. I was there at lunchtime one day and she popped them in the highchairs and starred feeding directly from the saucepan. I was quite shocked but as she explained it was so much easier for her with two as she just didn’t have enough hands to cope with 2 plates and 2 babies without a huge mess! I then decided it was genius in her situation! Her hubby was in the legion so she was doing it mainly on her own.
Reminds me of the (very) politically incorrect Army slang for "MRE"s (Meals Ready to Eat) - Meals Rejected by Ethiopians…
Definitive Academie answer!
In English, if such a thing is needed, as host/hostess with guest diners waiting, we might hold an upturned hand towards the meal setting and say say “Please” (not too enthusiastically!) and smile.
Best homes (and restaurants) in UK would have the waiter simply bow and back away. Saying “Enjoy!” is not U but forgiven for foreigners. 
This always sounds weird to me as an English speaker as at first sight it appears to translate as “Good Disgust”. 
There’s an apocryphal story about a Queen (in most accounts, Queen Victoria) entertaining guests and everyone being served prawns, which, according to etiquette, should be broken open with the hands. Each diner was provided with a small bowl of warm water to rinse their fingers. But at this meal, a foreign dignitary picked up his finger bowl and drank from it. The Queen, without missing a beat, picked up hers and drank from it, too.
Etiquette is more about care and consideration and all of those things that allow everyone to sit down at the table as equals, to share food and to feel comfortable doing it.
I remember in Beirut, my four year old brother picked the flower petals out of his finger bowl and ate them. At least it kept him quiet.
“You Will Eat!!”
was barked at us when our food was served… at a small auberge/resto… during our very first visit to France…
The Owner/waiter… was trying to make us feel at home by using his English language skills
(it could almost have been a scene out of “Allo, Allo…” )
The next morning, when I ventured down a little early… Madame (his Mother) was making croissants and despite neither of us being able to really understand the other… she patiently showed me "how it was done… " and we eventually had these delicious goodies for breakfast … yummy
It’s called ‘chabrol’ round here, but we don’t do it quite like that, or with that in the bowl. 
I was wondering what the tick in a box meant in the displayed title of this thread.
It seems to be an indication that @ChrisMann answered the question correctly.
Moreover, the site software tells me that
Répondez uniquement si :
which seems a bit crotchety 
My question is who awards the tick?
I note that @lebeuil1 (who asked the original question) “liked” Chris’s answer, so is that the explanation?
Well naturally I am right about everything…
However rather than some Olympian judgement being handed down, I suspect we have a bit of AI jiggery-pokery going on, but perhaps the Forum Gurus can tell us more?
No AI jiggery-pokery going on, just a manual tick box.