For every campaign under the "Leads" tab, there is now a new "Filters" button that allows you to filter leads based on lead status, lead owner, and special conditions including:

- Opened an email

- Clicked a link

- Replied to an email

- Last contacted

You can then further filter, by adding conditions for the number of times these have occurred (how many times opened) and within a specific date range (in the past X days).

You can combine different conditions to filter out the leads, for example:
Opened an email 3 times in the past 7 days + clicked the link 3 times in the past 10 days - so you can follow up accordingly with these leads.