By default, Unito will automatically sync all opened tasks and issues when you create a new sync. But if you feel the need to also sync closed tasks/issues prior to the sync creation, there is a simple option to do so.
To enable this feature, go to your sync settings and under the "Filter tasks" tab, click on the little toggle beside "include closed issues". And that's all there is to it. This can be enabled for either one or the two projects.