[CSS Help] Show/Hide based on input value

input.sheet-NewDieType[value^="1"] + *.sheet-dtypedropdown {
	display:inline-block;
}

1. Set the value attribute of your checkbox to 1, and you'll get 1/0 rather than On/0.
2. The CSS attribute selector is only going to look at the what's hardcoded into the HTML, not what the attribute's current value is.

You can use a checkbox show/hide within a repeating section; it'll have to be either a single checkbox outside the section toggling all of the show/hides at once within the sections, or a checkbox in each repeating section item toggling elements only within that repeating section item. For example:

<input type="checkbox" class="check-toggle" name="attr_toggle" value="1" />
<fieldset class="repeating_example">
    <div>Always visible</div>
    <div class="example-toggle">Sometimes visible</div>
</fieldset>

.example-toggle { display: none; }
.check-toggle:checked ~ [data-groupname=repeating_example] > .repitem .example-toggle { display: block; }

versus:

<fieldset class="repeating_example">
    <input type="checkbox" class="check-toggle" name="attr_toggle" value="1" />
    <div>Always visible</div>
    <div class="example-toggle">Sometimes visible</div>
</fieldset>

.example-toggle { display: none; }
.check-toggle:checked ~ .example-toggle { display: block; }

The former would show all of the copies of "Sometimes visible" when you check the single checkbox. The latter would have multiple checkboxes, each displaying a single instance of "Sometimes visible" when checked.