You may enter a comma-separated list to retrieve multiple tournaments at once, but at most 5000 matches can be queried at a time.
Tournament names follow the same naming structure we use on the wiki, e.g. "LCK 2019 Summer," "LEC 2019 Summer Playoffs," etc. These calendars will not auto-update; instead you will have to re-generate them each time the schedule is updated. Remember flex scheduling will change the order of some games!
Instructions for importing to Google calendar can be found here (will also be available from the query result page).