Once you have created one or more subitem templates, you can apply them easily to the main task items in your board.
Step 1: To create subitems from templates, click Open to open the item page.
Step 2: Once in the Updates section, select the Subitem Templates app and choose the appropriate template from the list.
Step 3: Click the Apply button next to the template you want to use, and wait until the process of creation is completed:
Subitems will be created under the current item you are on.
Please do not close the app during the creation process as it may prevent some subitems from being created.