It seems that once you start the process of seeding a tournament, the invitations you sent are all deleted.
How then can I host an ongoing league where players can join and leave while the league is running?
I would like to second this as a crucial capability. Being able to add and remove a few players at a time on a round-to-round basis without having to start an entirely new tournament is necessary for ongoing competitions like the Transcontinental Ladder.
When stage (season) is finished, new players can be added/deleted - that's what I was told by CGE.
That's good to know... though the ability to edit the player roster after going into the seeding tool will be useful. I know I'll probably make mistakes, and not having the ability to make changes could pose problems for tournament moderators.
It seems like there's a timing issue if the only time a player can join is between rounds. There's (ideally) a narrow window between when the last round ends and the next one begins. If we have to wait until the round end, then wait new invitations are accepted, then this will lengthen the time between rounds.