Thanks for joining the thread, @kndzpntnr. I'm here now, and I'll ensure you can set different mark ups for different items in your QuickBooks Online (QBO) company.

Know that for this to work and for you to have the ability to set different markups for different items when you create invoices. You'll have to set different price rules. That said, you'll also have to set the price rules to be added individually to your product and service items. I'll gladly input the steps below so you can proceed.

If you've already enabled the Price rule feature in your company's Account and settings, you'll want to create new price rules and set them to different markups. Here's how:

1. Access your QuickBooks Online company.
2. On the upper-right corner, click the Gear icon and select All lists.
3. Choose Price Rules, and then click New Price rule.
4. Add a name for the rule, and select which customers you'd like the rule to apply.
5. In the Product and services field, click the dropdown arrow and then choose Select individually.
6. In the Price adjustment method, select Custom price per item.
7. input the necessary details in each remaining field.
8. Click Apply rule.

After this, proceed to add the product or services below. Here's how:

1. Click the Add product or service button.
2. Add all your products and services manually, and then add different amount in each of their ADJUSTED PRICE column.
3. Once done, click Save or Save and close.

Once everything is set, you can create an invoice and choose the mark up in the Rate column on each line item.

Please know that if you want to add different markups to different items, you'll need to create new price rules and add the product or service in which you want the price rule to affect. See this article for more information: Set price rules in QuickBooks Online.

In addition, I've got you this article to help you manage payments in QBO: Record invoice payments in QuickBooks Online.

You can also check this page in case you'd like to customize your sales forms and match them with your business in QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.

@kndzpntnr, If you need further assistance adding different markups to your items in QuickBooks. Feel free to get back to me by clicking the REPLY button below. You can also post here again if you have any additional QuickBooks-related concerns. I'll be more than happy to help you out again. Take care, and have a good one.