Why is the editor's menu button "hide tools" is missing in Internet Explorer 10

Question

We are using CONF release 5.5 since some weeks.

When editing pages there is a button "hide tools" in the editor on the right side (two arrows to top). The function is hiding the page's header to get more space on the screen. 
In FireFox 35 we can see use that button. Also Ctrl+Shift+F is doing the job as marked in the tooltip.

In IE10 there is no such button and also the key combination is not working.

Why and how to get the button?

Stefan Baader · Answer

That issue came up again in our user community. I created https://support.atlassian.com/servicedesk/customer/portal/14/CSP-167342

Nobody can tell me why this feature has that behaviour and for what reason it will be removed. In our running CONF 5.5.7 it is available in FF and not available in IE. So users are complaining and struggling about. And they are right. Concerning usability this is a no-go

ivan · Answer

The confluence-editor-hide-tools plugin is disabled in IE.

From the source:

// IE is a no-go for now.
if (tinymce.isIE) {
    return;
}

Also, this plugin has been removed in Confluence 5.7 with the new lighter editor.