Hi, you don't have to use your inbound/outbound trips.

Keep in mind that they are not on top of the travel days but on 2 of the travel days that you use, you can use it in your home country too. Including to get from/to the airport if the train company that runs there is included.

Although called in and out days they are actually just 2 of the travel days (of your choice) where you can travel in your own country as freely as if you were in any other country in the network. You can cross border freely in either direction or even not at all. Interrail is only interested in supplying you with the appropriate number of train travel days, and has no interest in your other travel plans. 
 
In 2022 I used a 10 day in 2 months for 2 excursions where I flew out and returned by train (i.e. 2 inbound journeys) with no problem.

With a mobile pass the app manages the 2 days where you travel in your COR and, once you have used both it will not let you add any further journeys in your Country of Residence.