Read this in detail:
https://rabbitsindoors.weebly.com/greens--veggies.html
The key here is safely
introducing greens/veggies. The link explains how to do this. It assumes your rabbit is old enough to be introduced to greens. Once properly introduced, then greens should be fed every day. It doesn't matter whether that amount is fed all at one time or divided into a few different feedings throughout the day. It is a good idea to be consistent though since rabbits tend to like routine.
The amount is explained at the link. There are also two lists -- one showing greens that can be included every day. The other list is for occasional greens. So something from that occasional list can be offered once every several days. (Alternatively, you can offer something from that list every day for several days and then stop. Then wait a week or so before offering anything from that list again. In the meantime, you would use greens from the daily list.)
Hopefully the link will clarify what you're seeking.