Sure, but if I add too many features, I have to remove the easy at some point ;).
If you want more control, you can do that with my other tool: https://discuss.eroscripts.com/t/funscript-video-merger-splitter/87056
It also uses the same code to merge, so the result is exactly the same.
Just create a csv with the same video name and your desired speeds, hit merge and select the csv.
Like
video1.mp4 100
video1.mp4 100
video1.mp4 90
video1.mp4 120
video1.mp4 120
etc.