Adding keyboard layout not listed [or can't be found]

Hello respected ones!

I would like to ask if there is a way to add a keyboard layout that is not listed on system's keyboard option?

Actually it's like this, there is a writing system that I want to use but it is not listed on the keyboard layouts available in my kali linux system. The name of the writing system is called 'Tagbanwa or Aborlan (as what Gboard of google name it) it is one of the ancient scripts used by the ethnics in our country Philippines. One of the famous ancient writing system of our country named 'Baybayin' is already in Kali Linux system, I already added it, it is under 'Filipino' keyboard option. I've been looking for the Tagbanwa keyboard layout because I was hoping I can find it and I want to create a website with contents using the script. My system by the way can read the tagbanwa characters that we used to type on social media such as facebook, I copy-pasted the characters to my text editor, to my browser and even used it to some of my folders. My point is, the writing system is supported by kali linux. My problem is just I can't find the keyboard layout for it so I can use it and type (write) using it. Maybe you guys can help me about this one?

Again the name of the writing system (script) is 'Tagbanwa' or 'Aborlan', as it is named in Gboard of google. I need it to be added to my laptop so I can write using it. Please help me! :'(

Any information please tell me as well on how I can use the script in writing using my laptop. Thank you so much in advance! Much love and best regards!

Vyogi