Neovim with lazy.nvim has that by default (delay included).

I'm not Neovim person, but would you happen to know what plugin provides that feature?

Sorry I'm exhausted and lazy.nvim is the package manager, but I meant lazyvim which is the distribution. Within this distribution I'm pretty sure it's which-key that provides a popup. If I type <leader> it pops with suggestion (and a little icon in front of each indicating if the next key has sub-commands or not).

folke/which-key.nvim: https://github.com/folke/which-key.nvim :

> Customizable Layouts: choose from classic, modern, and helix presets or customize the window.

LazyVim keymaps: https://www.lazyvim.org/keymaps