Found an interesting issue today. Wanted to place some CSS code in Content Editor Web Part (CEWP) and hide it, so that it won’t appear to end-users. I added a content editor web part, placed some CSS code, went to web part properties, oops! Hidden property under Layout is disabled (greyed out)!!
Cause: For some reason, SharePoint doesn’t allow us to hide web parts on publishing pages! So Content Editor Web Part’s Layout hidden property is disabled!!
Here is the workaround to fix SharePoint 2010 web part hidden grayed out: Just Append ToolPaneView=2 to the URL to open the page in Edit mode. E.g. https://sharepoint.crescent.com/sitepages/home.aspx?ToolPaneView=2
This opens Add Web Parts Pane, from there we can add new CEWP to bottom zone of the page (Verified in SharePoint 2010 web part hidden property is not greyed out this time!) and hide the web part with out any issue!