I can’t believe my luck but Custom Sort has officially been achieved.
Obsidian Bartender, a wonderful plugin that I already use for custom sorting of icons in the sidebar, has added Custom sorting to the file browser.
Example:
In order to install Obsidian Bartender, either manually install the plugin or use BRAT and search for nothingislist/obsidian-bartender.
Once you’ve installed it, click the official Sort button in the file browser and hit “Custom” at the bottom.
My Obsidian wishlist is nearly complete.
Thank you @NothingIsLost!