Kdenlve doesn't allow a full control of the interlacement method of clips, projects and export.

The option to deinterlace footages to match other clips in a project is pretty important for several reasons:

• It happens frequently that you have to mix up different materials coming from different sources in the same project, mostly when you're working for television or documentary
• You can have a 50% speed smooth playback by using the 50/60 fields as deinterlaced interpolated frames
• You can interlace slow motion 50/60fps to create standard speed interlaced footages -

The option to control the field priority (during the export and in the project settings) is important too, as the interlaced format is still pretty common in television production. Different broadcasters can ask you to match their standards and some use the lower field as first some other the upper one.

My suggestions about are:

1. To add a contextual menu to the clips in which we have the following options:
   1. Deinterlace (with one or more way to do it)
   2. Deinterlace b0b (create one frame from every field by interpolating the missing line) for a perfect 50% slow-motion
   3. Interlace by speed up 200% (for 50/60fps footages)
   4. Reverse fields priority

2. To add to the profiles in the project settings panel not just always the voice "progressive" but also the voices "Lower/Pair field priority" - "Upper/Odd field priority". A person can select the priority who match better the majority of the assets in the project.
3. To add to the profiles in the rendering panel the same options I just described. By this feature, you can export straight in all the timeline in the final format as requested even if the original clip has an opposite priority (the rendering shift just one field and reverse the priority when it needs to reverse the interlacing method)
4. To add to the profiles in the rendering panel the options "deinterlace" when you need to deinterlace a full timeline of interlaced clips in an interlaced project.