This idea has been merged into another idea. To comment or vote on this idea, please visit EMP1-I-772 Add folders to templates.
Adding the ability to filter or search for a particular campaign or email template would be extremely useful. As the number of campaigns and email templates grows, it becomes increasing difficult and time consuming to find what we're looking for. I think any team that has more than a handful of campaigns or email templates would benefit from this feature which would be expected in any modern web app. It could work similarly to how the filters for Forms work.
Also, for Campaigns, please allow for searches by email subject line — it's common to be asked to edit an email campaign and the only reference given is the subject line.