[UPDATE]: Sorting function has been updated to this mechanism - Data fields for Sorting (xviz.com)
Here is a quick workaround to sort your tasks based on the start date/End date. This method can also be used to sort tasks based on other categories. For instance, let’s consider the below sample data.
I have sorted the data based on the start date. You can sort the columns in your Excel based on your requirement and add a S.No column to the table
In Power BI, Add the S.No column in the Display Measures field (Screenshot A) and sort the Visual based on the S.No (Screenshot B)
You can hide the S.no column from the visual by turning off the S.no column in the display measures field
Your tasks will now be sorted based on the start date.