Thank you for your first post, wiseearth. Let me provide some insights about journal entries.

You can select Add lines to insert more lines when recording journal entries in QuickBooks Online (QBO). To remove the extra fields, tap on Clear lines as well. 

In your case, can you tell me more about inserting a single-line option for journal entries? This way, I'll be able to gather and share with you the right amount of information. You may also attach screenshots for visual reference.

Your reply is much appreciated. Just leave a comment below. I'm just a few clicks away from assisting your once more. Have a good one!