What does this option do? What problem is it supposed to solve?
Suggestion about Custom Game seek.

We have problems finding players for custom games most of the time.
and this option can find players who are interested to the seeks. The private seek need not be excluded.
Public seeks can be shown to online players. Maybe a little more classification on where they can see the seek can be given by the admins.

So you could invite two players, and seek for one more to complete a 4 players board and start the game, correct?

The bulk of the work would be on the UI that would show the available custom games to players searching for a game. A player should be able to review all options selected, before deciding to join a custom game. Then the rating-range settings of all players should also be considered, because a player should not be allowed to join if his rating was outside the range of a player that has already joined. It's a lot of work to do, but surely would increase massively the popularity of custom games.

@MainframeSupertasker, thank you. We are working on this now, but I don't think we'll use Watch tab for that. Imagine that there are 5 custom games, in this case Top Games won't be visible. But yes, we are going to create a list of public custom games waiting for players (anyone who wants) to join.
I think an open custom game seek option can solve a problem. It can look like that of above.