Let me share an idea about what the "Not Specified" item is on the report.
Since journal entry has two accounts associated with, that is the reason why it's labeled as "Not Specified" on the report. I can definitely see how this feature would be useful. As a team with a massive road-map, we have to pick new features based on the value they’ll add to the most users possible .
I recommend sending this request straight to our product engineers through feedback. We share recent happenings and future developments on our blog. Through this, you're able to get the latest news about QuickBooks and what our Product Care Team is working on.