Some suggestions

  • cancel on all operations (Ctrl Z)
  • add audio and video markers
  • add ‘go to marker’
  • to be able to reunite a video after the cuts
  • keeping the arrow keys pressed advances the movie continuously (now only one frame at a time)
  • after simple operations, such as cuts, you can quickly export the movie without recompression
  • be able to vary the audio level in the timeline by inserting key points
  • automatically calculate the new dimensions of the exported video by entering a single value (width or height)
  • add the bitrate value in the audio property

Many of these are redundant and already on

to be able to reunite a video after the cuts

Already possible using merge in the clip context menu if the clips are contiguous from same source. Non-contiguous, non-same source is called “grouping.”

keeping the arrow keys pressed advances the movie continuously (now only one frame at a time)

works already, but may depend on what has focus

after simple operations, such as cuts, you can quickly export the movie without recompression

It is impossible to do with the mixture of media and sources that both Playlist and Timeline in Shotcut permits. It would have to be a dedicated new UI panel and workflow within Shotcut, but there are other tools that do this, and not everything needs to be in one tool. Also, it very problematic and has a high support cost. I never plan to work on it, and if someone contributes it, I would be highly critical and quite possibly reject it as something I do not want to support (a lot of contributors do not stay around to provide support and fix bugs).

be able to vary the audio level in the timeline by inserting key points

use Keyframes

add the bitrate value in the audio property

Use Properties > menu > More Information

See Properties > menu > Extract Sub-clip…