Frankly, for a facility as useful as content controls, Microsoft's implementation of the means of entering them is weak at best.

To overcome the limitations I produced https://www.gmayor.com/insert_content_control_addin.htm which makes the insertion of the types of controls most used (and mapped versions of those controls) a breeze and it retains preferences. You can enter your own placeholder text (or type the placeholder text in the document and select it before running the process and it will use that text as placeholder) and if you click in such a field, whatever you have used as placeholder text, the whole of that placeholder text is selected.

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Graham Mayor - MS MVP (Word) (2002-2019)
Visit my web site for more programming tips and ready made processes www.gmayor.com