Content:
1. What is a card subtask?
2. How to create a subtask?
3. How do you display subtasks at the closed card view?
4. How to edit a subtask?
5. How to change the order of the subtasks?
1. What is a card subtask?
Creating subtasks is the simplest level of a task breakdown.
The subtask can be considered as a smaller task, which is part of a more complex one.
In other words, it is an element of completing a larger task (img.1). Subtasks are useful when you have multiple items to do on a given card to show their progress.
The subtask is created at a card level and has two states: checked and non-checked. It does not inherit the card properties and can be completed by different users.
Img.1
2. How to create a subtask?
The Subtask tab stores all subtasks that belong to the card.
Open the Kanban card and go to the Subtask tab or right-click on the card to open the Context menu -> select Subtasks. When there are no subtasks created, the Subtask tab displays a single value 0.
In the Subtask tab panel, users can write, post, assign, edit and delete subtasks.
To create a subtask:
Enter the subtask name in the text box (1) → use "Add Subtask" button (2)
or
CTRL + ENTER to add a new subtask to the card (img.2).
Optional:
- You can assign the subtask to a registered Kanbanize user → select a name from the dropdown list with board assignees. Note: The subtask assignee can be different from the card assignee.
- You can also attach a file to your subtask -> click on the Attachment icon and upload a file from your computer/cloud storage.
Img.2
The subtasks that you have created appear as a checklist in the panel (img.3).
When a user has completed a subtask, they have to tick it off in order to mark the task as completed.
The Subtask tab displays the number of total Subtasks in the card and lets you see the number of completed Subtasks vs total Subtask from anywhere in the card.
For example, when 2 out of 3 subtasks are completed the numerical fraction displays 2/3.
To focus on uncompleted tasks, a user can hide completed Subtasks using the button in the top right corner (img.3).
Hover over a subtask to see: Subtask ID, Date/time of creation and completion.
Img.3
3. How do you display subtasks at the closed card view?
Users have to individually configure the card view in order to make the subtasks visible at the closed card preview.
Go to the sidebar at the right side of your board interface and click on the Configure Card View icon to open the Card settings panel.
In the Card Settings panel, you first have to checkmark the Show Subtasks option.
Then you have to select any of the three Subtask view alternatives:
- Progress bar
- One per row
- Only unfinished
Option 1: Progress bar
If you select the first choice, you will see the subtask count. It displays completed subtasks vs the total number of subtasks. Click the preview icon, and the system will redirect you to the Subtask tab. 
Option 2: One per row
If you select the second choice, the system displays all subtasks in a row.
The biggest advantage with this preview option is that you can easily checkmark a subtask as completed without opening the Subtask tab. This preview provides a clear picture of all subtasks that belong to the card and their current status.
Moreover, you can quickly create new subtasks, without opening the Subtasks tab. Just enter the subtask in the New subtask text box at the bottom of the card and click Enter to add it to the card
Option 3: Only Unfinished
If users select "Only unfinished", the system will automatically hide subtasks that are checked as completed on the card preview. Note that all subtasks remain available in the Subtask tab of the card. 
4. How to edit a Subtask?
Open the subtask tab -> hover over a subtask that is not finished yet and use the Options icon (the three dots) to:
- edit a subtask
- convert a subtask to card
- delete a subtask
You can double click a subtask to enable the edit mode.
Note: If you want to edit/convert/delete a subtask that is marked as completed, you have to first remove the check mark and use the navigation described above.
5. How to change the order of the subtasks?
Very often when creating and working with subtasks, users have to change their sequence order.
To change the order of the subtask, you have to open the Subtask tab and hover over the existing subtasks to see the Reorder icon.
Just drag & drop them in any order you feel is best.
Please, read the next article to learn how to convert a subtask into a card.