I'm here to offer some insight about setting up the markup percentage on parts in QuickBooks Online.
Setting up the markup percentage by parts isn't currently offered in QuickBooks Online. You'll need to edit the markup percentage in every transaction. 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. Your feedback and product suggestions will be used for coaching for our product developers. We aren't able to tell when a feature will be available. 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.