The built-in libraries are initially located inside of the Arduino install folder. The architecture independent ones are at Arduino/libraries. The architecture dependent ones are in Arduino/hardware/arduino/{architecture}/libraries. If you update the library to a newer version in Library Manager then the new version is installed to the libraries subfolder of your sketchbook folder. When the same library is present in the install folder and the sketchbook folder the library in the sketchbook folder takes precedent. Libraries included with other hardware cores that are installed using Boards Manager are located in your arduino15 folder at arduino15/packages/{vendor}/hardware/{architecture}/{version}/libraries. For me the The Audio library did not come installed either with the IDE or with the SAM Boards installation. I had to install it using Library Manager so it is located in {sketchbook}/libraries.
You can open the library files and modify using any text editor. If you want to delete the library just delete its folder and then restart the Arduino IDE.
pert - thank you for the reply. But when I look in the library directory I only see libraries I have installed, not the ones that come pre-installed. When I search my entire MacAir hard drive, I can not find any instances of Wire.h, yet I know it exists somewhere in some form because I am using it.
Again, I have searched my entire hard drive and can't find the "embedded" libraries.
On my computer(Windows 64 bit) wire is in:
Due: C:\Users\per\AppData\Local\Arduino15\packages\arduino\hardware\sam\1.6.4\libraries\Wire
Zero: C:\Users\per\AppData\Local\Arduino15\packages\arduino\hardware\samd\1.6.1\libraries\Wire
AVR(Uno/Mega/Leonardo/Etc.): C:\Program Files (x86)\arduino-nightly\hardware\arduino\avr\libraries\Wire
If you have updated to a new version of Arduino AVR Boards in Boards Manager then the AVR version of Wire would be in:
C:\Users\per\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.6.8\libraries\Wire
This is a series of experimental changes to the IDE. This will be about quick access to libraries. "CTRL+3", type "libs". Select a library press "ENTER" to see the online reference, or press "SHIFT-ENTER" to open the source code folder in IE/Finder/XXXX