I appreciate what you've done so far, AndieT. I understand how beneficial it is for your business to have this feature in QuickBooks Online (QBO).

As of the moment, the dropdown option for mark-up is currently unavailable. As a workaround, you can manually add a mark-up on your invoices by adding a line item. Here's how:

1. Hover to Add product or service dropdown and select Add subtotal.
2. Then Select a product/service dropdown and click +Add new.
3. Choose Inventory and name it as markup for identification.
4. Enter the Initial quantity on hand and As of date.
5. Once done, click Save and close.

While this option isn't available, I recommend sending feedback directly to our engineers so that it'll be included in the upcoming updates.

Here's how:

1. Go to the Gear icon, and select Feedback.
2. Enter your comments or product suggestions.
3. Then select Next to submit feedback.

Once submitted, you can track your feature request through QBO Feature Requests website.

In addition, you can check out this article if you want to personalize and add specific info to your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online.

I'll keep an eye out for your reply. If you have further questions about managing your invoices or any QuickBooks-related concerns, feel free to include them in the comments. We're here to assist you 24/7.