In ArcMap and ArcGIS Pro, when you run a Geoprocessing tool the details of that run are stored in the Geoprocessing Results or History, and that prior run can then be reviewed and rerun in the future without having to set all of the parameters.
Example: ArcGIS Pro History.
In ArcGIS Online Geoprocessing is called Analysis. However, there does not appear to be any Analysis History, yet, in ArcGIS Online. Then, you have to re-enter all of the parameters from scratch, every time you run the Analysis tool.
Please add Analysis History to ArcGIS Online.