Creating a dynamic task list for recurring reports in Power Query (Power BI)

I want to home in on what I think is the main complexity of your request and for which other specialized PM/task software is typically used.

It's not calculating end dates from start+duration. It's not handling your natural language column (e.g., "20th of previous month" would need to be converted upstream into Month Offset, Day Offset columns, which are then easy inputs for calculating a date).

It's the dependencies between your tasks. While it's technically possible in Power Query, it would be much simpler to input all the tasks+dependencies into some other software, have that calculate all start/end WD, then export your task list for visualization in Power BI.

That said, it would be an interesting problem to tackle. However, I'm still unsure on what is your desired output. Do you basically want something like the below, where the Start WD and End WD are calculated for all recurrences up to some end date or duration (which you have not specified btw, unless you want this paramaterized or something)?

Note: assume next WD for specified dates when they are non-WD (e.g. 12/20/2025)