Incidentally, I ran into a bad issue yesterday. When dragging a vertical video into VMS 16, it would automatically make it horizontal, which doesn't work. Any attempts to rotate the video upright via pan/crop or Motion Track caused VMS to crash. What I ended up doing was rendering it as-is, and then using that render to rotate it upright. For some reason it didn't like the raw video from my cell phone, but only when recorded vertically.
In File>Render as..., select one of the render template (usually Magix AVC > one of Internet template), then do customize on resolution size, to fit for tiktok's requirement, then save the new render setting as new template.