At the moment the Voukoder codec only appears in the Menu that is in the File / Render As...
Please, if possible, in a future version add Voukoder in the Menu Tools / Render to New Track ...
And in the Menu Tools / Selectively Prerender Video.
However, it is important to know that certain file formats rendered by Voukoder cannot be imported into the timeline using the Render to New Track and Selectively Prerender Video options, as Vegas does not offer import support for AV1, FFV1, HAP, VP8 formats and VP9. Vegas will support importing to the timeline only the formats H264 (X264), ProRes, Quick Time Animation and HEVC (X265) only in mp4 container.
For these reasons I'm not sure if this request is a good idea. Please, analise this question to see if it is worth the effort. If it is not possible or if it is not worth the effort, it will be understandable.