Thanks for getting back to us. I'm here to provide some update about Invoice via QuickBooks Online (QBO) Mobile app.
As of now, editing an item for Invoice via Mobile app is a known issue in (QBO), our engineers are currently investigating and working on an immediate fix. I suggest reaching out to our Customer Care Team so they can add your account to the list of affected users. This way, you'll be notified of any updates on the progress of the investigation via email.