I wouldn't bother to list any countries transited while traveling. Generally if you are making a connection by air, you don't really ever even cross through immigration and just held on the airport side.
Now if you make a stop for a day or more while traveling, I would do my best to list all those countries.
I've done a lot of cruising and really had to wrack my brain for ports I've visited. However under travel history, I just listed things like
Brazil - Amazon Cruise - Mo/Yr
Then in the "other information" section, I gave a quick list of ports visited.
Thanks, and when it asks
Have you ever travelled outside your country of residence, excluding the UK, in the last 10 years?
Does this mean my current country of residence or my country of residence at the time of the trip? I've lived in the USA for the last three years but visited there many times prior to becoming resident. Do I need to list all of the pre-resident trips?