Hello, I need to edit an include .h file in an arduino library installed using library manager. More precisely, I need to change something like the line #define I2C_ADDRESS 0x3c to #define I2C_ADDRESS 0x3a. How do I do this? Thanks in advance.

Try advanced scripting. There is example for similar case Redirecting...

jcw December 2, 2021, 1:58pm 2

See a related note: How to amend a file in a library - #2 by jcw

If that can’t be used, I’d create a copy of the library in your lib/ dir, which should cause PIO to find that one instead of downloading it. Then you can change that copy.

Edit Arduino library file installed using library manager