Nelio Popups allows you to set a cookie when a popup opens. Go to Nelio Popups » All Popups and edit the one you want. In the editor sidebar, go to the Settings panel, and open the Advanced tab. There, locate the toggle ‘Create custom cookie when popup opens’ and activate it.
By default, the toggle is deactivates. No cookie will be created on popup open. But you can activate this setting. If you do so, you must indicate the name of the cookie that will be created when the popup opens.
By default, the cookie that is created is valid for the current session. If you want it to last more time, just deactivate the toggle ‘Session cookie’ and the a field to set the cookie expiration will appear. The default value for non-session cookies is of 1 month. This can be changed by plugin users to a different value. Acceptable units of time include seconds, minutes, hours, days and months.
Cookies can be useful to trigger new popups or perform other functions when they exist.