Young me is envious. I downloaded or typed in, I forget which, some monitor program[0] that I used a lot, but loading it was far more manual than what you described and was basically impossible to load while another machine code (i.e. non-BASIC) program was running.

I still learned so much from typing short programs into it. I talked my parents into buying me an assembler so that I could make changes without re-typing a whole program.

[0] https://www.c64-wiki.com/wiki/Machine_Code_Monitor