I made a userscript that I wanted to share. With this script you can generate the text to speech audio for your lesson and it will automatically upload the audio and generate the timestamps.
You do need a Microsoft Azure account to be able to use their neural text to speech, but the process is not very difficult and the selection of voices you can use is great. They do have a free tier in which you can get up to 500k characters per month of text to speech and I believe they give you $200 credit when you sign up if you ever exceed this limit.
Anyways, I made this script because I am studying Japanese and the generated audio and timestamp does not sync very well which makes it hard to use the audio when using sentence viewer. This script fixes that issue and allows me to use voices that I like from Microsoft Azure.