To save your MIDI mapping, save your Ableton project. All mapping is saved with it. However, note that this will not be kept for your next project, and you will need to complete mappings again. There are a couple of other methods you can use to save mappings - the first is to use a MIDI Remote script, also known as a Control Surface script. These are similar to MIDI mappings, but they are unique and separate from projects. You can load these from the Preferences menu, and all the mappings you have created will automap to your controller.   There are a couple of disadvantages to using this method.   If you are a musician and not a coder, this is not for you as you need to have coding knowledge of Python. Some third-party apps that automatically create MIDI scripts for you are available, but that is for another article! Alternatively, you can create mappings and save them to a separate project. This way, all mappings are kept in one place. If you choose to use this method, you will need to open this project, use it as your starting point, and begin your creative process.    Save this as your current default to avoid having to recreate MIDI mappings for each project. To do this, navigate to Preferences > File / Folder, and click the 'Save current set as default' button.