Below is a thread that is kept for several months in this matter:
viewtopic.php?f=265&t=142632

PS
I think Kdenlive is a great project, and the Kdenlive Team is a team of professionals, which is why it is completely incomprehensible that we are asking for this amendment for so many months and there is no positive reaction on your part.
It's frustrating to install another version with hope, which has new interesting solutions, and then return to the one - old version, that works correctly...

This start/stop whit space bar is still an issue only on the windows version. The developers are aware but they don’t know from where it comes. On Linux it works.