build assemblies

Let me give you some insights into what’s causing lag in your QuickBooks Desktop (QBDT), @BernieJ.
 
Sometimes, lag issues are caused by the saved data in the system or your platform just needs an update. As of now, you can try updating your QBDT to its latest release. Here’s how to update:
 

1. In your QuickBooks Desktop, go to the Help menu.
2. Select the Update QuickBooks Desktop button.
3. Click on the Options column and enter the necessary fields.
4. Select the Update now button, tick the box for Reset Update.
5. Click on the Get Updates button and confirm.

 
While waiting for the update to finish, do not make any changes in your QBDT until you can see a prompt message that the update is done. I added a screenshot below for your reference.
 

 
Also, you can check this article if you still encounter lag issues while working in QuickBooks Desktop: System requirements for QuickBooks 2020 and Enterprise Solutions 20.0.
 
Count me in whenever you need further assistance. Have a wonderful day!