The menu, and a price that knows what time it is
Categories, dishes, variants, a price per channel, and a schedule — happy hour is a window on the menu, not a second menu.
The menu is the outlet's, set from its own screen: categories, dishes, variants and modifiers, the station each fires to, the tax group each belongs to, and a price per sales channel — dine-in, room service, takeaway, an aggregator.
Time
A category can carry a schedule: breakfast until eleven, the bar after six, Sunday brunch. The live menu shows what the clock allows. Happy hour is the same mechanism with a price: a window on a category with its own price, in force for its hours, and the bill says which price applied.
Per channel
The aggregators are marked up; room service carries a different service charge; takeaway carries no service charge. A price per channel on each dish, so the markup is a number on the menu, not a percentage somebody remembers.
Reading it
The POS reads the live menu for the outlet's clock; the aggregator door reads the channel's prices; the reports read the category and the item.