With RPi Full Fat Noobs you can add any Raspberry Pi Noobs OS to the offline installer
This is a simple python 2.7 script that downloads all necessary files of selected additional OS to Noobs for offline installation.
To run the script simply enter the following command in the terminal: python full_fat_noobs.py
The link to the OS json file is hardcoded on line 11 ('https://downloads.raspberrypi.org/os_list_v3.json')
The list of chosen OS to download is hardcoded on line 12 (myList=[1,5,8,11,13]) each number represents the index of the selected OS, to check all OS before selecting any, replace line 12 with: myList=[]
The downloader also enables auto-resume and auto-retry failed downloads by default; it can also detect whether server supports resume or not automatically.
Note: Windows Core requires an active internet connection, even if the files are downloaded for offline installation.