Video editing is generally not done in memory at all. The videos themselves sit on disk and are played back from disk, and the desired cuts/effects are composited on the fly.
For speed, an editing app may also produce lower-res versions in memory for quick seeking and smooth playback, as a kind of quick preview. But that's easy to control how much memory you allocate for that, and even those previews can be stored or cached on disk.
Video editing is not especially memory-bound on modern machines. It's much more CPU/GPU-bound when it comes to applying effects, and IO-bound (including decoding-bound) when it comes to larger videos like 4K and 8K.
For speed, an editing app may also produce lower-res versions in memory for quick seeking and smooth playback, as a kind of quick preview. But that's easy to control how much memory you allocate for that, and even those previews can be stored or cached on disk.
Video editing is not especially memory-bound on modern machines. It's much more CPU/GPU-bound when it comes to applying effects, and IO-bound (including decoding-bound) when it comes to larger videos like 4K and 8K.