You can reference controls from any screen, so don't feel limited to have them all on one.
I do not recommend the global variable approach, because you'll either need one per screen load, or will be updating the same variable each time.
Instead, I recommend you name your dropdowns, boxes, inputs, etc. with clear names. Like 'drpState' and 'txtCity' if you had a drop-down for state and a text input for city.
Then, once the user is done, add a function to a button to collect all the controls into a collection.
Collect ( colName, { inputColumn1: drpState.Selected.Text, inputColumn2: txtCity.Text } )
Then make sure to Reset all the controls, and navigate then back to the start. Each time they finish and click the button, a new row will be added.
You can then add other columns, like the User().FullName, etc. to further add context.
Good luck!