You can easily add existing tasks as subtasks to any other task in Wrike. If needed, you can add the same task to multiple parent tasks.
Drag and drop in List view:
Navigate to the folder, project, or space containing the task you want to convert and then switch to List view.
Click and hold the task you want to convert (from the List view panel).
Drag the task you want to convert and drop it over the task where it should be a subtask.
From Task view:
Open the task where you want to add a task as a subtask.
Click Add subtask (or if there are already existing subtasks click + New task at the bottom of the subtask list).
Begin typing the name of the task you want to convert, or you can paste the tasks permalink there.
Click the task name when it appears in the drop-down list.
If you need to attach the same subtask to multiple parent tasks you can do that from Task view. Just repeat the steps described above with each parent task separately.
From Table view:
Navigate to the folder, project, or space containing the task you want to convert and then switch to Table view.
Find the task you need in the table.
Right-click the task and select Add subtask.
Enter the subtask permalink to the field and press Enter.
If you want to create a subtask from Table view, follow the steps described above, but instead of permalink enter the name for the new task into the field.