Nuturing Campaign

There isn't an across the board way to suppress emails from all but one campaign, at least not in a way I know of.

You could suppress all of them by using the Blacklist option, or you could have some field you check before sending (your remove from flow example) but as you said, that would have to be in every campaign.

There are some options:

1. create a custom field which gets stamped when someone enters Nurture, and then make sure other campaigns Exclude leads where that is filled in.

2. Use Lead Status = Nurturing to flag leads in those nurture campaigns. Then make sure your other campaigns exclude those leads.

There should be no reason to do a Remove From Flow unless all of your leads are already in a nurturing campaign and you want to extract them from that existing campaign first.

What josh said, or add all leads in that nurturing campaign to a static list and exclude any members of that list from other emails. Or you can just add flow steps that suspend the marketing of every lead in the campaign before and after every email.