What is the difference between Vignette (on image adjustment) & Vignette Effect (on Alpha/Transform)? Tell me about those effects and describe them?
One is built in and the other is provided through frei0r. Here you can find more info about each effect:
If I may add: Vignette — Kdenlive Manual 23.04 documentation
The official Kdenlive documentation explains both effects and points out the small differences
You can make very nice vignettes with both. But “Vignette Effect” has more settings, especially you can move the position of the vignette with x and y, which is sometimes very advantageous.
Try it out, the two effects explain themselves. Personally, I always use only Vignette Effect.