Current effect parameter has some limitations that we would like to fix in relation to the dopesheet goal (#1400) This lists some of the changes we plan to do for this task: Refactor [xml effects description](https://invent.kde.org/multimedia/kdenlive/-/blob/master/data/effects/README.md?ref_type=heads) to allow: - [ ] better validation checks - [ ] better design for widgets handling multiple parameters, for example a `Point` widget to indicate a coordinate on screen, that would be represented in the effect by 2 parameters: `x`, `y`. That means xml parameters are not a 1:1 map of MLT params, but can represent several MLT params in one xml param. - [ ] allow some kind of groups, that could allow to have a header text for some parameters: for example for hsl primaries, we have multiple values for hue, same for saturation and value. Having a way to groupe them could help. - [ ] Allow parameters that can have multiple entries. For example some parameters could take an arbitrary number of points or of gradients. - [ ] Introduce new widgets for gradients and points - [ ] Ensure existing widgets are well optimized to use the strict minimum space - [ ] Think about how we want to display comments and param descriptions in the UI - [ ] Add a tag to inform the app if a parameter can be displayed on monitor or not (by default all animated rectangles and all points should show up, but also in some cases rotation or more) Some open questions: - Should we use MLT's widget description ?