Editora 0.20.0. Archived, so links from that release keep working. Read the 0.24.0 page →
View: Toggle Hidden Files in Project Tree
view.toggleProjectHidden Show or hide hidden (dot) files and folders in the Project tool window
How to run it
Open the command palette (M-x in the Emacs keymap) and search for View: Toggle Hidden Files in Project Tree, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.