You can drag and drop a task, folder, or project to move it to a different folder/project or convert a task into a subtask.
Click and hold a task, folder, or project's row number on the left side of the view.
Drag the item:
Over the title of a task, folder, or project into which you want to move it.
Or, if a task, folder, or project's task list is expanded, anywhere in the list. You'll see a blue line and border around the title of the task, folder, or project, where it'll be moved.
Release your mouse.
The item is moved to a new location and its position in the table depends on the applied sorting option.
To drag and drop a range of tasks at once, click the first task in a range, press and hold Shift on your keyboard, and click the last task in the range. Note that these tasks must be on the same level (so you can't have a task from a folder and a task from its subfolder in the same selection).