Heya mate, Bohemian sent me a little plugin that you can use to restore the functionality. I made a small tweak to it to also include layers that are marked for export.

https://github.com/KevinGutowski/Select-All-Slices/raw/master/Select%20All%20Slices%20in%20Page.sketchplugin.zip

I remember over in the SpecFM Slack channel you talked about Ash Thorp's UI course from LearnSquared. I was wondering why you are taking the course - what are you hoping to get out of it (Do you have any ideas for your project yet)? For me, I'm interested in learning about how UI can capture imagination and techniques that I can bring into building usable systems.