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Make sure you have displayed all relevant data in 2D mode before you start the digitizing. The Quick digitizer is started from Tools -> Quick Digitizing.
The quick digitizer menu
By default the digitized line is saved in the workspace. This means you will have to copy it from the workspace and into the project. You can also use the Save digitized line also in folder to save it directly in the project. Just tick the check box and browse in the folder you would like to save it to.
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