Connorrc, you can teach a sequence of commands (2 is easy, 3 is more difficult without another learning remote) to a single command name by using the learn in RAW mode, but your timing must be consistent since it will ask you to repeat the sequence before it will accept it. Use the Device > Learn IR, but click "Custom" at the bottom of the page to enable learning in RAW mode. Don't forget to type something in the "Learn a New Command" window (at the bottom), else you new command name will default to "MyNewCommand". Then map that new command name to a key. Note: You can also use the Activity Sequence feature (under the Activity Customize Buttons) to map a sequence of up to 5 commands to a single key.

However, for your matrix switch case, why not just add another switch device to your configuration. The 1st one to send the input selection command, and the 2nd one to send the output selection command. Or, (with only one switch device to send the input selection command), use the activity start/end macro (Custom Actions) feature to send the switch output selection command. The activity start/end Custom Actions feature becomes available when you review the settings for the activity and select "Yes, but I want to add more control of options and devices for this Activity". Click next/save several times until you get to the activity Custom Actions feature.

In this case you don't need to - it applies only when you need more than 5 commands to be sent.
You can set up a Sequence made up of the two commands.