Bind Templates with Projects
Bind templates with projects option is located on the
Templates configuration page in Time Tracker (templates.php).

Bind templates with projects option in Time Tracker
When selected, it allows you to associate each template with a set of currently active projects, similarly to project-task association. Enable the option and click Save. Now when you add or edit a template, you can bind projects with it.

Binding a new template to active projects
In the screenshot above, a set of checkboxes for active projects is available. Use them to bind a template with projects.
When entering time, only associated templates get into the Template dropdown for each selected project. This filters out unnecessary templates from projects that do not require them.

Only associated templates appear in the Templates dropdown in Time Tracker
Time Tracker User Guide