This app seems quite useful even if you have some other video editing app... you could use it to convert videos to lots of different formats... including QuickTime Animation with an alpha channel and WebM with an alpha channel... for both of those, you just choose one of the included presets.
You could also make your own preset for ProRes with an alpha channel if you choose the ProRes preset, make sure "Advanced" is selected, go to "Other" and change the text in the box to these lines:
Then, just save that as a preset.
It seems good for converting videos to HEVC and AV 1 too... it has the "Quality-based VBR" option were you can set the "Quality" and it changes it to CRF... HandBrake recommends something between 18-28 for HEVC (setting the "Quality" to something between 65% to 47% in Shotcut would set the CRF to that)... so the "Quality" set to 55% (CRF 23) will probably be a good balance for most videos and for more high quality videos you can raise it a bit or lower it a bit for lower quality videos... for lower resolution videos that would be upscaled, it would be a good idea to use somewhat higher quality settings than for 4k, if it's a high quality SD video.
If you want a "slow" preset for HEVC or H.264 (to encode it more slowly to get a somewhat higher quality), just change one of the existing presets (just change the "preset=medium" to "preset=slow" under "Other") and save it as a new one.
Also, you can edit WebM and even WMV directly in it, without having to convert it first.
The interface maybe seems kind of "clunky", like it often seem to be the case with apps that are ported from Linux... but it's a useful app.
So 5 stars for the usefulness... although the interface could probably be significantly improved... but at least it doesn't require XQuartz like Linux ports sometimes do... so it seems like a relatively decent Linux port.