I use a variety of software on a day to day basis, but what I use for videos in particular are:
Video Editing: mostly kdenlive, but I do have DaVinci Resolve but I hardly use it
Thumbnails i use Affinity to make them, but my knowledge of it is very limited
Other Software i use rufus, balena etcher or ventoy for bootable USBs, NTLite for custom windows isos, darktable for editing RAW photos taken with my 550D, and probably more but my mind's blank :(