It was [[https://de.wikipedia.org/w/index.php?title=Wikipedia:Technik/Text/Edit/VisualEditor/R%C3%BCckmeldungen&oldid=178186818#Wikitext_%E2%86%94_VisualEditor|reported]] that when switching from visual to source code editing, the checkbox which allows to permanently disable the switch notification is invisible:
{F20908580}
The relevant part of the HTML:
```
<span class="oo-ui-widget oo-ui-widget-enabled oo-ui-inputWidget oo-ui-checkboxInputWidget" aria-disabled="false">
<input tabindex="0" aria-disabled="false" class="oo-ui-inputWidget-input" value="" id="ooui-1" type="checkbox">
<span class="oo-ui-checkboxInputWidget-checkIcon oo-ui-widget oo-ui-widget-enabled oo-ui-iconElement oo-ui-iconElement-icon oo-ui-icon-check oo-ui-iconWidget oo-ui-image-invert" aria-disabled="false"></span>
</span>
```
The problematic CSS is this rule which is in effect when it should not be:
```
.oo-ui-widget .oo-ui-iconElement-icon, .oo-ui-widget .oo-ui-indicatorElement-indicator, .oo-ui-widget.oo-ui-iconElement .oo-ui-widget .oo-ui-iconElement-icon, .oo-ui-widget.oo-ui-indicatorElement .oo-ui-widget .oo-ui-indicatorElement-indicator {
display: none;
}
```
How to reproduce the problem:
# Log in with a new user account (older accounts usually have disabled this notification permanently)
# Open a random article in visual editing mode
# Use the pen in the upper right-hand corner of the editor to switch to source code editing
# Observe that the checkbox is invisible