You can use Jitsi Meet API to create Jitsi Meet video conferences with custom GUI.
Jitsi Meet uses Browserify. If you want to make changes in the code you need to install Browserify. Browserify requires nodejs.
On Debian/Ubuntu systems, the required packages can be installed with:
sudo apt-get install npm nodejs
To build the Lib Jitsi Meet, just type
npm install
Please use the Jitsi dev mailing list to discuss feature requests before opening an issue on Github.