Custom CSS tab missing

I'd like to modify a three years old template, setting the #maikncontent width from 1024 to 1200.
But the Custom CSS tab for #maikncontent is missing (see the image) . More, is missing for each block in Template Creator CK. The only Custom CSS present is the main one. (Parameters → Custom CSS).
How can I have the #maikncontent Custom CSS tab back?

Please, note that inspecting my website I can find the active rule in template.css: So, I did define it, but now I don't know how to modify it, since I don't like to put this rule within the general Custom CSS frame.
My website: www.fimaviaggieturismo.it/
Thank you!

An update.
To temporarily fix the problem, I wrote in the Parameters → Custom CSS the rule but it produces no effect. In fact, this rule is not showed by the Inspector.
It seems to be an issue with the custom css engine. Box, I need a pit stop...

Hi
the custom css is loaded

*/ Larghezza maincontent */
#maincontent > .inner {
max-width: 1200px !important;
}

your comment is wrong :

*/ Larghezza maincontent */

shall be

/* Larghezza maincontent */

I will check for the maincontent custom css missing, but to manage the template width, you shall do it the Parameters >> page >> template width
CEd

Evidently I need a pit stop for fine tuning my brain...
I made the comment correct and the rule worked. Thank you.

Regarding your suggestion, I like to set the full width for the template and the 1200 width for the maincontent. In this way, I can easily publish full width modules above or below the content (menus, banners, CTA, footer and so on).
This is a workflow I'm comfortable with.

Thank you for investigate the custom css tab missing.

ok I understand
this makes sense

Another update...
I compared my fimaviaggieturismo template with another more recent (but the Template Creator CK version is the same).
The Custom Styles Creator of the older site lacks both some options of the Formatting tab (as you can see in the images) and the Custom CSS tab.