Oculus Virtualkeyboard Custom

I am currently conducting user experience comparative research related to virtual keyboard input interaction in VR environments using Oculus. To facilitate my research, I am looking to make some modifications to the virtual keyboard provided by Oculus. For example, I would like to implement changes like inputting special characters when holding a key for an extended period.

Therefore, I have a couple of questions:

1. Is it possible to modify the Oculus virtual keyboard? Are there editable assets or prefabs available for this purpose?

2. If modification is possible, where can I access and edit the code related to input actions and outputs?

If you have any experience customizing the Oculus virtual keyboard or any guidance to offer, please assist me. Your help will be greatly appreciated.