In previous versions of Kdenlive in some effects like pan & zoom and in the transitions Affine and Composite you had this little red rectangle to modify size and position.
For 0.7.8 I tried to make editing this type of parameter more convenient and efficient:
All the options previously available but hidden do now take most space in the effect stack.
The red rectangle disappeared therefore you can now drag and resize your item directly on the monitor.
Find out more in my blog post on "On-Monitor" Effects