@vizou I'm not sure what you are referring to, it isn't clear what you are trying to do.
Content template functionality is available on the Post Title, Post Body, and in the 1.5 development release the Post Custom Field.
If you are trying to use content template functionality on the Post Tag field, it isn't supported.
If you are trying to pre-populate a Post Tag field the only way to do this is by using the Default Value functionality found under the Advanced tab when editing the field. It can also be pre-populated dynamically via the query string or by writing custom PHP.
Posted 9 years ago on Monday February 14, 2011 | Permalink