• We have also the same task here: https://phabricator.kde.org/T1951 under the different heading "fast transition".
• To me, the term "in-track transition" (similar to "same track transition") is more descriptive than a "fast" transition. So as I think that we will need to keep the overall term "transition" as is for some time at least, I would like to opt for "in-track transition" then.
• In-track transitions are only these ones I would think; the rationale would be that these transitions are not keyframable, but instead inherently dependent on time:
  1. dissolve
  2. slide
  3. wipe
• I wouldn't count compositing transitions, such as affine, as in-track transitions, as I'm failing to see how they could used without keyframes for time-dependent transitions like dissolve, etc.
• In-track transitions would help in some tricky situations that currently result in rather unwieldly track setups: in particular, when transitioning (wiping, ...) where at least one clip is not a simple clip, but already the result of compositing/blending. What is yet unclear to me: what would be the order of transition processing for in-track transitions? Especially, if there is a track above that gets composed onto the track containing the in-track transition?

• I apologize for adding a topic already exists.
• I already discussed several times about the name for the new transitions approach (when it'll be implemented) with Harald Albrecht. My point is that we can't change the name "transition" to compositing or blending modes to the current transitions environment soon. This for avoiding confusion in people who has already habit with Kdenlive. The problem exists when people come from other softwares to Kdenlive and this is what I hope mostly. Since late 90's there are no more video editing applications which use more tracks for transitions. Of course you can create crossdissolve and other effects by using more tracks and keyframes but this is not what people are used to. My proposal was "fast transitions" mostly for 2 reasons: to help people who come from other software where it's the standard way to use a single track and to give the idea that Kdenlive has a fast workflow for performing this kind of feature. Actually one of the most important thing about to use transitions on a single track is that you can apply them by using the keyboard by using a simple shortcut hit. Anyway the name is not the main problem. So if the majority prefer single track transition I'm not here for loosing time. What is important is to implement the feature.

• The typology of transitions used by the main softwares are:

1. - Cross dissolve
2. - Cross zoom
3. - Wipe
4. - Iris
5. - Slide
6. - 3D motion

• Affine is not a transition but a blending mode (that means Affine is a way how two clips are blended together)

• Transitions in only one track are very useful in a lot of situations and they are really faster to apply than a blending method with keyframes. If you want to revert it or to manage the order of transition processing for creating a different setup from the default setting you can use the transition panel. For which concern how to composite a track who contains a transition onto another track I don't understand the problem. Actually nothing change. You have to use the standard alpha management or you have to add a "Transtion" (read: blending method) to the upper track for compositing it whit the lower one.

For all my opinions and my approach to this topic please read:
https://old.kdenlive.org/node/9458#trans

Really well written, massimostella. I have to agree, this would be a significant leap towards modernizing this component of Kdenlive. So many prodigious changes have taken place to improve Kdenlive for users; this would make it that much more amazing.