If you find yourself at a repast with nothing to do, wash their dishes.
During a repast, the bereaved are stumbling through the worst grief of their lives. In the midst of this, they are throwing a party. It’s hard to manage both. People do it, somehow, but it adds a lot of stress on top of a bad situation.
If there are dishes in the sink, wash them. After the dishes are dried and put away, organize the food. Put the plates and silverware in one spot, near where people start down the line. Put the light stuff first (salads), followed by casseroles and pasta dishes, followed by meats. Put them all along the edge of table, like you might see at a Home Town Buffet, so people can walk down and take a little from each dish. Remove covers from containers and put each cover right underneath its container.
If someone was smart enough to bring paper plates, then go get the kitchen trash can. Empty it. Put a new bag in. Then put the kitchen trash can by the food table. People will get the idea.
Do a very slow walk around the house. Grab up trash, dirty plates, cups, empty dishes. Then go wash some more dishes.
Anybody who notices you taking care of things will assume you’re supposed to be doing it (because, really, who would volunteer for this?).
You can probably wrap up everything I’ve listed in 45 minutes – an hour if there are a lotta lotta dishes. When you’re done, have a drink, since you’ve earned it. Or leave, because you’ve made your appearance.