In order to be able to add an element to the template in the future, and have it be inherited by all templates and pages derived from that template, the "Click to insert new element" that you use must not have been previously used to add an element to any of the derived templates or pages. In other words, the act of inserting a new element breaks inheritance for that whole cell. In order to prevent such "hijacking" of the "Click to insert new element" at the page or derived template level, all of the tabular layouts in the template should be locked-down also, so that the "Click to insert new element" is not displayed while in "Author" mode on the derived page or template:
Go to the template.
Select "Work on this Page" or "Work on this Page (All Changes)"; scroll as needed to see the "Tabular Layout Element" icon, , that appears on the top left corner of the table that includes the element that should be revised only from within the template. In general, you will need to do this for every layout element except for those that are undefined in order to contain page-specific content. In class, you will choose the layout for the page as a whole, using the icon that is immediately under the logo graphic in the header at the top-left corner of the page.
Click on the "Tabular Layout Element" icon, that you have identified.
From the drop down menu, click on "more," and then select the option "Element Inheritance Security."
Under the "Restrictions" section click on the "Change" button.
In order to fully preserve inheritance, lock all the access rights to the element by checking all the check boxes ("Author/Edit," "Design," "Style," and "Admin").
Click on the "Save" button.
Click on the "Close" button.
No yellow work-in-progress icon appears: the changes made take effect immediately, and are not recorded in the Version History.
From now on, while you are working on any page or derived template that was created from this template, you will notice that you have no access to edit those layout properties.