While holding shift and the right mouse button to select multiple clips, there is a massive lag while moving a large amount of items. I tried this both on linux and windows with similar results in terms of lag. I also don’t have a slow computer.
Try this out yourself and see if you can reproduce it, place an image into the timeline and then copy paste it until you reach the 30 minute mark, then select them all, it should then say that you’ve selected around 350 items, then try moving all of those clips and see if there is a massive lag.
The ability to smoothly move a large amount of items is important with big projects if you need to correct things.
I also tried this experiment with sony vegas 10, I could copy paste the 5 second image until it reached 10 hours in the timeline and the performance would be still acceptable. So this tells me that this is probably fixable for kdenlive.
Now maybe it is also just a problem with my computer, in case it isn’t I urge someone to tell developers this.