Customize template of dhtmlx scheduler

Hello. I want to be able to add textboxes and remove some elements on the scheduler but it seems like everything is on the minified javascript.
How will I be able to add or remove elements from the scheduler?

Thank you.

most of scheduler UI can be customized via public api, modifying source codes for this is not recommended.
If you’re talking about changing controls of the lightbox/details form - please check this article
or please clarify if you mean something else