Not everyone knows that saving a video is not such an easy task as saving a Word document. It is resource-intensive calculations of all effects, overlays, and encoding video and audio with a special codec. Here's what dramatically affects the speed of saving:
Hardware acceleration availability and use (graphics card dependent). There is a checkmark in the save video dialog. The speed with and without acceleration can differ significantly.
Resolution and number of frames per second (FPS) of the project itself. 4K video will be saved several times slower than FullHD. The project resolution is written to the left of the Make Video button. You can click there to change it, by the way.
If you edit a video on a laptop - is it plugged in (much faster) or running on battery power (slower).
The speed of the media where the source files are located and where the final video file is saved. If the source files are on a flash drive or sd card, video saving is much slower, and various floating errors may occur. Ideally, use an SSD as a storage.
Some effects (tab "Effects") can noticeably increase the encoding time of the final video. Using timers, counters, frame counter also slows down saving.