Editora 0.16.0. Archived, so links from that release keep working. Read the 0.18.5 page →
Appearance: Set Font Size…
appearance.setFontSize Set the editor font size in points.
How to run it
Open the command palette (M-x in the Emacs keymap) and search for Appearance: Set Font Size…, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.