It looks like you're using Method for QuickBooks Online. In this case, I don't believe that the J table is currently in-use. If you're planning on building a custom workflow, I'd recommend that you instead create your own ob Type custom table for this.
It's al ways a possibility that Intuit will implement this table in the future for QBO. It's best practice to avoid using these currently not-in-use tables for custom data, as this cou ld cause problems with the sync should the table ever be implemented in the future. I hope this helps.