I'm trying to figure if it's possible to have one train line use any available track on a station without having to directly assign it. So if I have Station A with 2 tracks available (1 and 2), and Station B with 2 tracks available (3 and 4), how can I assign a line to do this? So if a train goes to Station A and track 1 is in use, it should go to track 2. If it goes to Station B and track 4 is in use, it should use track 3. Basically an IF statement for stations with multiple tracks. Is it possible to do this?

As far as I know it is not possible. A line is assigned to a specific station platform.
It issue is debated many times in official and steam forum. Some agree with it and some don't.
Personally I agree with this design. In our daily life a train always go to an assigned platform in normal situation. It only change when there is a malfunction train blocking the platform or other reason makes the platform unavailable.
Surely in some large terminal station, passenger has to stay in the waiting area, wait for an announcement telling them go to which platform.
We in HK trains always go into assigned platform, but our neighbor China has the dramatic platform assignment in large terminal station.
On the other hand I'm going to try if a platform can serve multiple lines. It should reduce number of platform needed...

Train Fever and Railroads are different scale games. Railroads is an industry simulator and it's about getting things where they need to go to keep industries profitable without dealing with the specifics. Train fever works at a much lower level as a time sensitive route scheduler. It's much more like Cities in Motion (With a bit of a city builder thrown in) than it is like the Tycoon railroad games that SMR came from.