This needs the libmlt update which I sent in SR#1130521.

- Update to 23.11.29:
Improvements:
* Added Crop:Rectangle > Apply to Source button. This button is only enabled when the aspect ratio of the
source media matches your project’s Video Mode because it is impossible to include the black padding that
Shotcut adds to a source. This feature is the primary way to simply “crop a video.” You do not need to use the
timeline for this. You can simply:
1. set Settings > Video Mode to Automatic,
2. open a video file,
3. add the Crop: Rectangle video filter,
4. adjust the rectangle control in the player,
5. click Apply to Source in the Filters panel,
6. choose Yes in the dialog asking to change the Video Mode, and
7. Export.
* Added Opacity to GPS Text, Text: Simple, and Timer filters.
* Improved performance of Timeline > Zoom.
* Added rectangular selection to Timeline.
* Added Settings > Timeline > Rectangle Select.
This is on by default, and scrubbing with the mouse on the timeline requires clicking near the play head.
When this is on, hold Shift to turn it off temporarily. When this is off, hold Shift to temporarily turn it
on.
* Changed the Smooth keyframe type to avoid overshoots and cusps.
This only applies to new projects made with this and future versions. Thus, the behavior of smooth keyframes
made with an earlier version remains the same for compatibility reasons.
* Added Ease In, Ease Out, and Ease In/Out to Keyframes.
This also changes the appearance of keyframes in the timeline view of Keyframes to make it more clear where
the behavior applies - between keyframes. Remember this: when thinking about “in” or “out”, for Shotcut “in”
refers to the beginning of something - a clip, filter, or parameter between keyframes. And “out” refers to
the end of something. So, this is not easing into a keyframe and easing out of a keyframe. Rather, it is
easing into or out of the change/segment/span/tween of a parameter between keyframes.
* Added Properties > View Bitrate….