I need to modify a library (flavortext.h)

Projects Programming
7

I don't know if it will fit in a Micro, so I don't know if you can test it without PROGMEM.

This is PROGMEM: https://www.arduino.cc/reference/en/language/variables/utilities/progmem/
You can try a few things to understand it. It is not changing a single line.

The output is written to a char array.
The String is used temporarily, and mainly for the easter egg.

With the define set to 67 and with 68 texts, then the last one is not used.

A better way is to add a end-marker in the text, but the code gets bigger.
An end-marker can be anything that is not normal text. For example empty string or a -1 or a # or whatever:

char myData[][20] =
{
  "Hello",
  "World",
  "",               // empty string as end marker
};