This feature is a REAL PAIN in the back side sometimes.
I can result in one losing all file edits inadvertently.
It would be better if the IDE asked you if you wanted to load external file changes and gave you the option to say no - do not load them.
I use that feature all the time. I checked "Use External Editor" in preferences, and any changes made in the external editor are automatically loaded. If you’re not using this feature, you’ll need to stick to just the Arduino IDE and avoid external editors.
Hint: Do not have more than one .ino file in the sketch folder. The IDE will combine them, which can lead to confusion and drive you bonkers.
Having it ask to load each external file individually would be a real pain. Instead, it automatically loads all the selected header files, the associated .cpp files, and several other files that help define the specific Arduino board you're using. These files vary between different Arduino models.
I use Geany as my external editor and keep most of the library files in the sketch folder, as I often modify them. This approach prevents issues when libraries are updated. It’s not uncommon for me to have a dozen or more files open as I work on a project. Keeping library files local also lets me review their content, see how to call their functions, and understand what they return.
Note that this is only present in the Arduino IDE 1.x preferences. Arduino IDE 2.x always picks up external changes to sketch files that are in a saved state, without requiring the user to first enable this behavior via a preference.
That I did not know as I have not switched to the 2.x IDEs. Thanks
"Having it ask to load each external file individually would be a real pain. "
Why can't it be an option in preferences!
Use or don't use it - your choice.