There is no search or filter function for the categories available.
This is just a simple information when scrolling through the sounds.
From the newest manual version (3.5), page 61:
SOUND CATEGORY allows you to assign the current preset to one of 32 pre-defined sound categories. This function is intended to assist in organizing presets for quick identification when auditioning sounds. This is especially useful in conjunction with the Voyager Editor/Librarian software.
Remember, that the first hardware revision of the Voyager had only 128 presets. And there was no other true analog synth with patch memory and categories on the market then.
The seven sound banks were introduced with rev. 3 hardware and software version 3.0.
The SoundTower editor is able to sort them by category.
If you have the latest* Voyager firmware update installed you can scroll through all the sounds in a category by pushing the two buttons under the LCD at the same time then hitting an arrow button right or left ~ check the update dox for actual key names & step-by-step method
Over the holidays I sat down and went through all 800+ presets, and manually categorized any that seemed promising (wrote down in a notebook) by musical function (drones, leads, bass, bells, weird piano, etc.). Also noted which were responsive to velocity and aftertouch.
Thanks for the tip though about category browse on the Voyager (without using Soundtower). I’ll probably make another pass through the presets to see if I can find something to use as a launching point for a duduk-like lead tone.