It likely is possible to do this. I currently do not have any example of this specifically. But I like the idea and have to note it down as something to dive into deeper.
Another name for what you are looking for is ‘incremental load/refresh’. This currently isn’t really possible in Power BI.
I discussed this here, but have not been able to showcase a good solution (mainly as there are so many variations in what could be required…it’s just not that easy)
How hard is it to actually save it into excel right now. If it’s not that difficult, personally I wouldn’t get caught up in doing this in Power BI as it’s making your life more difficult than it needs to be.
Think of excel as just another staging area for your data. It’s just like a database really, but a much easier place to locate and manage data tables now.
Chrs
Sam