I have 200 vault dwellers plus a line of 10 waiting outside of my vault. I try to open a lunchbox that I got from a weekly report and it says that i cannot because, "There are too many Dwellers in the waiting line." I can't find anyway to open the box or kick dwellers out of the waiting line and I also can't add them to my vault since i have the "maximum number of Dwellers allowed by Vault-Tec."

it seems reasonable that game refuse to open new lunchbox which may cointain a dweller that will be queued outside of vault, if the queue is already full. Kill off some existing dwellers and clear the waiting queue. Then the lunchbox will open.

You can't open lunch boxes if you do not have room for new dwellers in the line outside the vault.

Makes sense yea. I wouldn't even try it if it was possible, since I might miss out on an awesome legendary dweller. The fact that you can't instantly kill/evict dwellers from your vault or from the line is an issue though.

Just put your weakest dweller in a production room by him/herself and repeatedly rush the room until an incident finally kills your sacrifice off. Remove the corpse (obviously, don't resurect), then move one of the people outside waiting for a spot into your vault and you should be able to open that lunchbox. Hopefully, you don't have any pregnant dwellers or you have have to repeat this operation a number of times.

If you get a legendary dweller, you will have to execute another of your dwellers to make room for him/her.