One of the best features in Vegas – scripts. They allow to increase the speed of editing process and save you from tedious work. There are some good paid tools. I use Vegasaur ( https://vegasaur.com ). It contains many helpful tools. Among them is Quick Properties tool that allows to change properties of multiple events, create transitions, place events on the timeline etc. You can freely download it and use for one month of trial period.
sfl file contains media markers (or project markers after rendering) and Vegas WILL NOT rebuild them (unlike sfk, which stores audio peaks). So if you don’t need media markers – you can safely remove them.
Scripts greatly simplify this task.
You can freely download and try Vegasaur ( https://vegasaur.com )
It includes the Quick Properties tool, that perfectly solves your problem