The page where you want to show all the courses. This is the page connected with BuddyPress at WP admin - Settings - BuddyPress - Pages - Course. When you enable WP admin - WPLMS - Course manager - redirect course categories/levels to directory this setting becomes important. The slug of this page also sets the url of the course. To edit the page in Elementor, you will need to disconnect the page from Buddypress and after editing , reconnect it with buddypress.