Can we update the dataset without deleting and adding again?

Typically, I work with Excel or Power BI Desktop programs and build my data model there. You can, under specific circumstances, add a column for instance and the next time you refresh, it will be added to your data model. This does not tend to work if you create calculated columns. You have to remove the calculated columns and then refresh and then add the columns back.

If you do it this way, update the data model and then load the PBIX or Excel file and overwrite the old data set, you will not break all of your reports, dashboards, etc.