The variable websitetoolbar.ini[CustomTemplateSettings].IncludeInView is reset in the default configuration file shipped with the ezwt extension :

websitetoolbar.ini

Other extensions are allowed to provide elements of GUI for this toolbar, through creating a couple of templates and configuring a local websitetoolbar.ini.append.php.

Example for ezmultiupload :

[CustomTemplateSettings]
CustomTemplateList[]=ezmultiupload
IncludeInView[ezmultiupload]=full

Depending on the load order of extensions, the IncludeInView configuration directive was emptied by ezwt/settings/websitetoolbar.ini, blocking the load of any other GUi element for the Website Toolbar.