Hi there, @Anonymous.

Allow me to step in and share some insights about changing product/service on invoice line item without deleting other information. 

Since this is how QuickBooks is designed at this time, we can try the workaround provided by our Community Backer on this thread. 

I'm taking note of this request and will pass it along here in my end.

That said, if there's something you need, please visit us again in the Community. I'll be here to help.