Add Transitions
You can download and install transitions from the KDE Store[[1]], or uninstall previously installed transitions.

In the properties panel of the composite transition, click on the edit-download Download button, and Kdenlive opens a dialog window with the KDE Store contents of available wipes.

Change the view mode: 
Sort the display: 

Hover over the wipe you want to download and click the Install button.
[[1]]
Kdenlive has a direct link to the KDE Store from where you can download and install new transitions in form of luma files (greyscale images of type .pgm). If you have an active Internet connection, Kdenlive queries the KDE Store for all of the luma files available and opens a dialog window.
*[RGB]: Red Green Blue
*[VFX]: Visual Effects
*[feathering]: Smoothing or blurring the edges of a feature