This simple utility takes as input the textfile generated by the [Export...] button in Audacity's Analyze>Plot spectrum... view, and produces another textfile can be conveniently imported as a preset ...

Can't easily reproduce. I had 3 tracks, 4-5 clips total, some of them displayed as Spectrum. I was trying to select the gap between 0.000 and the start of the first track, and selecting accross tracks ...