You don't need to put everything in one file. Just add a new unit (a source code file), and separate your code by functional use into those distinct units.

If you have enough units that are all related and you want to separate the code even further, put them into their own packages and import them into other projects.

You can be disorganized in any programming environment. It's your job as the programmer to name things correctly and break apart common code or task into their own reusable compartments.