Hi @raassd ,
Are you using an editable gallery in your App?
Maybe you could try to use Patch() function to create record in another data source.
Patch function in Power Apps (contains video) - Power Apps | Microsoft Docs
I have made a simple test for your reference.
1. Here are my lists.

2. Here is my App.
Patch(List1,Gallery4.Selected,{Customertype:{Value:ComboBox1.Selected.Value},Comments:TextInput1.Text});
Set(varrecord,LookUp(List1,Gallery4.Selected.ID=ID));
Patch(List2,Defaults(List2),{Title:varrecord.Title,Email:varrecord.ApprovalEmail,'Serial number':varrecord.Serialnumber,
type:{Value:varrecord.Customertype.Value},Comments:varrecord.Comments})

Result:

Best Regards,
Charlie Choi