Hi Enzo.
The point of the reset button is to reset the process so that it can start from the beginning. If you make a change and want to continue, you can select another stage, right click, and choose "Set Next Stage". This will redirect the flow of the process to start from that stage but without resetting all of the data items.
For example, if you made a change in stage 18 and want to go back to the prior stage and run through stage 18 again to see the what happens, you could right click stage 17, select "Set Next Stage", and then when you continue, the flow would start from stage 17.
Does that make sense?
jack