Editora 0.10.0. Archived, so links from that release keep working. Read the 0.18.3 page →
Markdown: Reset Preview Zoom
view.markdownZoomReset Reset the Markdown preview zoom.
How to run it
Open the command palette (M-x in the Emacs keymap) and search for Markdown: Reset Preview Zoom, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.