At any stage of building your chatbot, you can click the "Publish Draft" button at the top right to publish (save) your chatbot model.
Note: Clicking this button does not activate the Bot in channel conversations; it simply saves it in its latest version. If the Bot you are editing is not active, it will not be activated with this action. If the Bot you are editing is active, the changes made will be taken into account for future conversations.
If you want to enable the Bot to make it operational in channel conversations, you can do so by going back to the "Bot" section in the left sidebar and clicking the "Enable Bot" button.
You can confirm that the Bot is enabled by checking the status in the Bot section.