IMO, in Europe that would mostly be where a selected starter (first course) happens to be composed of salad-type ingredients.

Unless otherwise stated a salad is usually expected to be a side salad served alongside the main course (btw Americans seem to call a main course an entree - whereas what Europe calls an entree is usually a first course not a main course). If it's delivered as a side salad then it's quite possible for the main course, or entree to Americans, to be delivered and the salad to be delivered very shortly after. The salad is then mostly eaten alongside the main course although some customers may finish it just after.

Of course depending on the type of eatery and in which section of the menu the salad appears, can usually indicate situations where a salad is positioned as a main course... sorry, to Americans an entree..../ or a starter.... / or a side dish.

Depending on the restaurant, waiters may ask when you want a salad served if you order one, if they sense you might have a non-standard preference or expectation.