Need Jira tasks as subitems

We need the Jira tasks to be created as subitems of the “Build” item on our project board. I have managed to get the Jira tasks to create as items and then convert them to subitems using a marketplace app. However, once they are subitems, they no longer sync from Jira.
IAs a workaround, I set up a board specifically to hold the Jira tasks as items and manually create the corresponding subitems on the project board. Then, I thought we could use mirror columns to keep the items on this extra board synced to subitems on my project board. However, the mirror column on the project board subitem isn’t syncing from the item on the extra board