You should separate the user input from the datasource nanoflow.
First, my assumption is that the nanoflow executes a database retrieve. In that case use a microflow.
Next to that; you should create something like this
- Show a page/popup where user can enter the parameter values
- Create a page which contains a dataview with datasource context/entity where you collect the parameter
- Add a nested datagrid with a datasource microflow. This microflow starts with a input parameter of the object to get the user input.
- Add a retrieve as you have in your nanoflow and return the list.