Here's how you can achieve this using the This can be achieved using existing functionality of Issue Matrix (IM):
Create a separate IM field for sub-tasks.
Specify which columns are relevant to sub-tasks.
Add the new IM field as a column
...
in the Epic IM field.
The sub-tasks of each issue inside the epic
...
are shown on that line as well.
Check out this simple an example of on how it could look looks in the attached screenshot .below:
...
Please find Find the below example for reference:
Create
...
respective fields in the sub-task custom field as shown in the below screenshot.
...
...
Create respective fields in
...
Epic custom field as shown in the below screenshot.
...
Refer to the below gif for reference
...
.