Can I link tasks from different projects or link projects?

The tasks are specific to the project and you cannot link tasks from different projects.

The link between the tasks is made in the “When” view, for more information about the links between the tasks, click on the following link: Links and Milestones

You also cannot link projects, but you can view tasks from several different projects on the Gantt chart in multi-project views. Choose filters to choose the projects you want to appear in your Gantt chart.