IIRC, if one segment clears, you have some like 72 hours to decide whether or not to take it. So if one segment clears, you're at the mercy of other inventory being available to make it work as a connection.

That said, you can book any workable EWR-IAH or LGA-IAH or PHL-IAH segment or connections to make that work.

So if IAH-HNL clears, and EWR-IAH doesn't, but EWR-CLE-IAH is available, you can snag that, and keep the EWR-IAH waitlist rolling.

If you're on the A330 or 747 with DL, I would just keep that instead of playing this game, because it's a pain. And/or maybe waitlist EWR-HNL nonstop if that schedule works for you.