This is a quick and dirty copy-paste hack to get Password Manager and "about:config" functionality in webrunner 0.5: You will need to modify two files in the chrome/content directory as follows... Inside the statusbar tag in webrunner.xul (line 51) add the following:

 <statusbarpanel id="statusbar-tools" label="">
    <toolbarbutton type="menu">
        <menupopup id="tools-popup">
            <menuitem id='menu_config' label='Advanced Config' oncommand="menuCommand('cmd_config');"/>
            <menuitem id='menu_passwordmanager' label='Password Manager' oncommand="menuCommand('cmd_passwordmanager');"/>
            <menuitem id='menu_jsconsole' label='JavaScript Console' oncommand="menuCommand('cmd_jsconsole');"/>
        </menupopup>
    </toolbarbutton>
  </statusbarpanel>

And add this to the end of webrunner.js:

/* advanced tools menu handler added by Mukunda Modell */
function menuCommand(cmd) {
	var winUrl;
	var features;
	if(cmd == 'cmd_config') {
		//show about:config (Advanced config)
		winUrl = "chrome://global/content/config.xul";
		features = "chrome,statusbar=yes,titlebar=yes,centerscreen,close=yes,modal=yes";
		window.open(winUrl,"About:Config",features);
	} else if (cmd == 'cmd_passwordmanager') {
		//show Password Manager dialog
		winUrl = "chrome://passwordmgr/content/passwordManager.xul";
		features = "chrome,statusbar=yes,titlebar=yes,close=yes,modal=yes";
		window.open(winUrl,"About:Config",features);
	} else if (cmd == 'cmd_pref') {
		winUrl = "chrome://webrunner/content/prefs.xul";
		features = "chrome,titlebar,toolbar,centerscreen,modal";
		window.openDialog(winUrl, "Preferences", features);
	} else if (cmd == 'cmd_jsconsole') {
		toJavaScriptConsole();
	}
}

Note: there is code to support JavaScript console, however, this is not working for me on Linux with the latest nightly builds of xulrunner. It should work on OS X though it might just be an issue with the default preferences. I will post an update here when I get it figured out. Enjoy!