I have QGIS 3.8.2 installed and started to look at the Geometry Generator. I have a layer of airline tracks and trying to create a curved line linking start and end points.
I did a lot of searching and found the followng code but when I apply this I get straight lines not curved lines like I have seen elsewhere.
make_line( start_point($geometry), centroid( offset_curve( $geometry, length($geometry)/-5.0 ) ), end_point($geometry) )
Hopefully its something simple that I am doing wrong.