Si on a une collection de recettes, de types 'entrée', 'apéritif', 'plat', 'dessert' etc etc, qu'est-ce que c'est le nom collectif pour ces choses? (si il existe)
C'est pour les catégories des recettes dans un site web Wordpress.
I would say Plat.
According to Larousse.fr :
Élément d'un repas : Un menu à trois plats.
The answer given here (i.e., plat) would probably be my first choice, primarily because it could easily apply to and include dishes that, although surely benefiting highly from skilled “presentation,” do not require “preparation” per se immediately prior to serving (such as plates of cheese or crudities).
However, in light of the fact that your question already includes plat, in both its title and its body, perhaps you were hoping to find something else and if that is the case, you might consider
[un/les] mets (invariably written with an “s”),
which according to its entry in my trusty hard copy of LE ROBERT-MICRO means:
Chacun des aliments qui entrent dans un repas.
Although the above definition of mets doesn’t seem to require/include the notion of “preparation,” my previously stated main reason for preferring "plat" and, more importantly, my resulting implied preference to hesitate using/proposing words that might imply the notion of "preparation," stems from the inclusion of the “preparation-required” notion of apprêté in the following Larousse.fr entry for the word (with emphasis added):
Tout aliment apprêté qu'on sert aux repas.
This n-gram could arguably be evidence that plat is indeed a better answer than mets (and as I go to post this, I’ve just noticed that you’ve wisely accepted it), for it shows that when prefaced by “Nos …” (which many restaurants do when heading a list/collection of their different [categories/types of] menu offerings), plat has been used slightly more often than mets (but see the opposite result when the two are combined with “et boissons”).
Nevertheless, in spite of n-grams' (and my own) preference for "Nos plats," “Nos mets” is also sometimes used by restaurateurs for this seemingly relevant purpose, as shown on this link to the website of Le New-Bisse, a pizzeria-pub located near the town of Granois (Savièse) in Switzerland.