VideoTik - Do I need to install the Mobile App to my phone to be able to publish videos to TikTok and Instagram?

Yes. You can schedule a post on TikTok and Instagram from the desktop VideoTik - Scheduler. You can also edit, delete and view all your created schedules, however, you still need to install the mobile app on your phone and keep it open/active for the notifications to take place. This type of automation is being controlled and regulated by the other platforms' (TikTok and Instagram) Terms of Service, that's why it is required to have the mobile app installed on your smartphone.