Editora 0.17.0. Archived, so links from that release keep working. Read the 0.18.5 page →
View: Toggle Completion Documentation
view.toggleCompletionDoc Show the documentation popup beside the completion list by default.
How to run it
Open the command palette (M-x in the Emacs keymap) and search for View: Toggle Completion Documentation, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.