If you get to a point in your work that you want to save, then you can save the "cursor state" of the program. File→Save Cursor State (or CTRL-S). You will be asked to give a name for the state, and a file called
filename.peach-cursor will be created.
You can then get back to exactly that state by reopening the cursor state file. Choose File→Open and select the cursor state file.
If you want to e-mail the dataset to someone open at a particular point, then you could send the dataset and an accompanying cursor state file.