Ask HN: Strategic planning tools for staff –> project assignments?

For work environments where there are multiple projects, what tool do you use to track/visualize staff assignment, so that external commitments can be tracked and that you're able to avoid over allocation? In particular, I'm looking for a system that helps plan and visualize work assignment at a strategic level, in days during a given week for one quarter out, or perhaps weeks by quarter for two years. It should provide a birds-eye view, a one pager at most, that an engineering manager could deliver to their executive team on a regular basis. Crucially, such a tool should not overlap with existing sprint-planning except perhaps on a very high level. Ideally it has an interactive interface that could be used during strategic planning sessions.

I'm asking because the tools I see are all too granular, modeling work as hours by day, rather than days by week.