You can configure elements whose enclosing text nodes should have whitespace preserved by going to: "Plugins->Plugin Options->XML Indenter".

On the options pane click the add button and in the dialog enter the qualified name of an element whose whitespace should be preserved.

A qualified name consists of the element name plus any namespace prefix if there is one. For example the XML Indenter comes preconfigured with whitespace preservation for elements named xsl:text, text and tspan.

You can remove elements from the list by selecting them and clicking the remove button.