Overall in my experience Workforce planning is something that organisation's do not generally do very well.
In part, this is due to one or more factors::
1. Reduced, or lack of strategy to know what you are planning against
2. Reduced, or lack of visibility into the amount of work required for the success of the strategy (if there is one)
3. Reduced, or lack of visibility into the strength of the workforce
Once you've established some of this information you'll need some tools, and here Power BI, Viva Insights, and Azure Synapse are your best friends when it comes to the analysis of some of this information.
We should also remember that a fuller Human Capital Management (HCM) solution also comes in the form of Budget planning in Dynamics Operations, this allows us to consume positions from the HR solution and start to make calculations on the costs of our growth if we take into consideration pension costs, national insurance and other cost components you want to define. All as standard.
For points 1 to 3, above. What do we do about those? Well...
Viva Goals - This will not let you down, put strategic goals in at the top and monitor strategy and key results by cascading across the organisation
What are we doing? A big one, telemetry depends on the vertical and industry, but typically production lines, ticket sales, product sales, projects, and backlogs. In Microsoft Dynamics there is a multitude of tools to draw this together from (all standard again).
Dynamics HR, got those skills surfaced in Dynamics HR and let people tell you their strengths through self-service. Let managers/others verify via workflows.
Depending on the nature of the business we may decide to incorporate, weather, pandemic, availability, and locale. The strongest solutions are those that best match the nature of business.
That said, all the planning in the world around the number of people needed, won't mean a darn thing, if your employee experience is flawed. Get that wrong and people will leave, and you will struggle to attract.