The Goal tag already exists. This tag could be added to tasks.
Then anyone can filter the workboard by clicking Open Tasks in the upper right corner, select Advanced Filter..., and set "Tags" to Goal.
If wanted, that resulting filter URL can also be added as a direct link in the sidebar of the workboard: On the left, click Manage , on the right select Edit Menu, on the right select Link.

Nothing for me left to do in this task, I guess... :)

+1 for Goal tagging. Filtering on a board could be made easier by adding a sidebar link similar to the ones on cloud-services-team (Kanban) which filter the board by team member assignment.

I experimented in the past with milestones like cloud-services-team (FY2017-18) to track Cloud Services annual plan projects, but that turned out to be awkward because of the way that Phabricator de-duplicates subproject tags. Things could be either on cloud-services-team (Kanban) or an annual goal tracking board, but not both at the same time. This could be worked around by making the annual plan tracking tag independent of a team's umbrella tag at the expense of a bit of global namespace clutter. If Phabricator were a canonical tracking system for annual plan work I would be interested in working on other organization ideas like a tag hierarchy that would allow organizing all Foundation tech team goals here. Today however there seems to be little appetite at the collective program management level to (ab)use Phabricator as a collective status reporting tool.