Bookmarks: Set Mnemonic
bookmarks.setMnemonic Give the bookmark at the cursor a one-character shortcut, so a single chord jumps back to it from anywhere in the project.
How to run it
Open the command palette (M-x in the Emacs keymap) and search for Bookmarks: Set Mnemonic, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.