Pages: Can I create text variables like in inDesign?
Sure, at least with the new version of Pages this is possible by using tables. You enter the value that you want to repeat into one (single field) table and you add a formula into the other (single field) table by entering = and then clicking into the source table (the first one). The result is a formula similar to this:

= Table 1::A1

This way the content of field A1 in table 1 is shown / repeated in table 2.

However, this does not work inline - only for full lines / paragraphs.

But if you want the same information (e.g. the document title) to be shown on each page or on several places in the document, this will do the trick.