I second the request. This was also described here:
File Explorer: Navigation Hotkeys
https://forum.obsidian.md/t/file-explorer-navigation-hotkeys/
… but someone deemed the Quick Explorer to be sufficient 
What I’m seeking is the ability to use e.g. CTRL+PgUp / CTRL+PgDwn to move up and down the file explorer without loosing focus from the contents of the document.
Just to give an example of a use case - I often catch myself going up and down a series of daily logs in search of a specific phrase or section - this can be done instantly with e.g. OneNote. Not the case with Obsidian currently (mouse clicks all the way 
).