I also use Excel for all my travel planning. I have a template. Well, I call it a template, it is actually a copy of the last trip but it means that all my trips are planned and documented the same way. It also means that at any time, either during the planning phase or during the trip itself, I have access to all the info about my train trips to/from the airport, parking, hotels, flights, seats, times, aircraft types, lounges etc... all on the one sheet.

There are trip planning products, such as TripIt, which I also use, but like the spreadsheet they only document what you have planned/booked.

I don't know of anything that can actually help with the scheduling and finding of flights other than ITA Matrix which is my "goto" place to find flights. Unfortunately Matrix does not have many of the Low-cost airlines such as Easyjet, Ryanair etc so it isn't the only solution.