Yes, there's a way to add a specific % increase across the entire inventory in QuickBooks, @muenstermann. Happy to share with you the complete details and steps. 

I agree that exporting and importing inventory whenever there are changes is time-consuming. That's why QuickBooks create a Price Rules beta feature. This functionality let you to enter a percentage (decrease and increase) for all of your products and services. 

To utilize this, let's turn it on first by following the instructions below: 

1. Go to the Gear icon, then choose Account and Settings. 
2. Select the Sales tab. 
3. Turn on the Price rules radio button in the 
4. Products and services section.
5. Click Save, then Done. 

After that, set up the price rule template. Do the following: 

1. Go to the Gear icon again and select All lists. 
2. Choose Price Rules and enter a unique name in the box. 
3. In the Product and services drop-down, pick All inventory.
4. Pick Percentage in the Price adjustment method field. 
5. Select Increase by and enter 5% in the Percentage field. 
6. Pick a Start and End date, then click Apply rule. 
7. Hit Save and close. 

For more knowledge about this feature, check out this link: Set price rules in QuickBooks Online.

Further, visit these articles below on how to modify items and run different inventory reports in QuickBooks: 

• Use reports to see your sales and inventory status
• Change product and service item types in QuickBooks Online

Let me know if you need further help in handling your inventory. Just tag my name, and I'll get back to you. Have a nice day ahead, muenstermann.