Recover variables lightbox for custome use

Hello Goodnight
I finally managed to customize the gantt lightbox, adding navs, but I have the following problem, how can I locate the variables that I must use the complete environment, to be able to manipulate them, as in the example that I have been working on.

Example link

Awaiting your comments and thanks in advance.

Hello Juan,
You need to find the HTML elements and obtain their values.
In your sample, you don’t have the phase section, so, it is expected, that it doesn’t work when you want to save the changes or add a new task.
If you add that section, everything should work correctly:

<div class="gantt_cal_ltext" style="height:38px;">
  <textarea id="input_1605990137099" name="phase" value="" ></textarea>

Here is the updated snippet: