Shotcut is a cross-platform video editing app from Meltytech LLC (Dan Dennedy) that offers a rich set of features, including native editing support for “oodles” of audio, video and image formats (including ProRes); native multitrack and multiformat timeline editing (no import required) with trimming, thumbnails and waveforms (cached); resolution support to 4K; audio mixing and video compositing across all tracks; append, insert, overwrite, lift, and delete (ripple) editing on the timeline; color correction and audio filters; the ability to create, play, edit, save, load, encode, and stream MLT XML playlists; encode/transcode, capture, streaming and batch encoding with job control; and much more.
Shotcut 20.12.17 is a free, open-source download for OS X 10.10 and up, Linux, and Windows. The latest release brings low-resolution previews, an audio pitch filter, and other improvements, while low-resolution proxies are planned for the months ahead.
Please remember that today there is still a processing cost to scale down the source video to the preview resolution. So, this is still not a silver-bullet, magical cure-all for performance issues. This feature will be more beneficial when low resolution proxies are used, which is planned for version 20.04 in April.