This is not a management room: you must prefix commands with !tg.

General

cancel - Cancel an ongoing action.
version - Get the bridge version.
help - Show this help message.

Authentication

ping - Check if you're logged into Telegram.
ping-bot - Get the info of the message relay Telegram bot.

Creating portals

bridge [id] - Bridge the current Matrix room to the Telegram chat with the given ID. The ID must be the prefixed version that you get with the /id command of the Telegram-side bot.

Portal management

config <help|subcommand> [...] - View or change per-portal settings.
delete-portal - Remove all users from the current portal room and forget the portal. Only works for group chats; to delete a private chat portal, simply leave the room.
unbridge - Remove puppets from the current portal room and forget the portal.

Miscellaneous

sync-state - Fetch Matrix room state to ensure the bridge has up-to-date info.
id - Get the ID of the Telegram chat where this room is bridged.
caption <caption> - Set a caption for the next image you send