Please place a Web link button on your toolbar.
When you click it, an Internet link for the task on which the cursor is located should open.
Better yet, make a user-configurable set of buttons on the toolbar. So that each user can choose which buttons should be visible.
There is an idea that is likely to be even better: Show clickable links in the task table · Issue #2235 · bardsoftware/ganttproject · GitHub
Let me disagree. The link column in the task table will take up much more screen space. One small button on the taskbar is much more economical. In addition, the link can only be opened for one task at a time. Therefore, it makes no sense to show a link for each task. If a link is set for the active task (on which the cursor is located), then the button should be colored. If the link is not installed, the button should be gray.