Replace room list filtering with search modal

[tulir]

Filtering is basically useless with spaces, should instead have a modal that always searches all rooms. That way it can also have better keybindings, like arrow navigation

[zouppen]

I agree. But it might also be a nice feature to search a room inside a space (for instance CCC event spaces which contain a large number of rooms), but not sure about what would be perfect UI design choice for that.