compression – How do you compress a HEVC video to a smaller HEVC video with FFmpeg while preserving transparency?

I have a few dozen videos encoded in HEVC that have a transparent background. They have tiny dimensions, but their file size is comparatively large. I need to re-encode them as new, smaller HEVC files, but I am struggling to do so while still retaining the transparency.

Is there a way achieve this? Thanks.

This is the closest I’ve managed to get so far based on other similar questions on here:

ffmpeg -i "InputFile.mov" -map 0 -c:v hevc -c:a copy -tag:v hvc1 "OutputFile.mov"