Applying for Belgian Schengen Visa (Business) - Do I need to pre-book local train tickets for a 1-day side trip?

Hey everyone, I’m putting together my itinerary for an upcoming Belgian Schengen visa interview for a work conference and need a quick sanity check on internal transport.

My schedule is fixed and I have my flights and accommodations booked for almost the entire stay. I fly into Brussels on Sunday, head straight to my conference city, and stay there for five nights. On Friday, I plan to visit a different city for a quick side trip, head back to Brussels on Saturday to stay at a hotel for one night, and fly home on Sunday.

Do I actually need to pre-book the inter-city train tickets within Belgium for the visa application, or is it fine to just list the routes on my travel itinerary without buying them yet? I already know I need to have my Friday night accommodation booked to show a complete lodging trail, but I want to make sure I won't get flagged for missing the local train tickets.

Thanks for any insight!