@Christine_New - I do hope (and anticipate) that they will eventually change this to allow you to include subtasks without excluding parent tasks.
However, in the meantime, there are a few ways to try and get you close to what you need, though none is perfect. Before I dive into detail about the options, could you clarify – what data are you trying to see? When people say they need to see their workload, sometimes they mean very different things:
Itemized list of tasks assigned, due during a given time period?
Estimated time field totals across a list of tasks, due during a given time period?
Estimated time field totals across a list of tasks, compared to capacity, due during a given time period, viewable day by day, in a timeline, as we see in the workload view?
If you need option 1 or 2, there are fairly simple ways to do this.
If you need option 3, it can still be done, but it will require some recurring manual work, or a custom automation using Zapier or Make.com.
Please let me know your thoughts so I can explain a solution that fits your needs.