It's not uncommon for something to change between when a campaign is scheduled and its actual deployment date. Currently, I don't see an easy/quick way to change a campaign from Scheduled back to Draft and vice versa.
In the Action (3-dots) Menu, it would super useful to have some kind of easy "pause" functionality that you could click to quickly pause a campaign before deployment rather than having to go into Edit the campaign and jump through a bunch of steps to get to the Schedule step and then remove the schedule information. And there's no Save button at that step, so you basically have to close out of the Campaign and double-check that its status has reverted to Draft in the Campaign index after the changes you made.
It's just a very clunky way of "un-scheduling" a Campaign, and sometimes this needs to be done in a hurry to stop a Campaign from sending.
Perhaps also adding a "Save as Draft" button to the Schedule step of Campaign setup would also be useful.
