We don’t currently have the functionality to import multiple lines for a single invoice unfortunately.
I’m not aware of any plans to introduce this. Generally features are driven by community demands. There is an existing topic for this here that you can add your vote to.
It is possible however by using our API. If you have coding knowledge, it’s well worth looking at. If you don’t, we have a Marketplace category on the forums you can post to, to find someone who could help with setting that up for you