In the Develop Module on the left side above the History panel is the <Snapshot> panel.
Click on the "+" sign and give your snapshot a descriptive name.
You can then make more edits to your photo but the snapshot will be preserved - even if you go back to 'Import" and start editing new from scratch.
In my view, the main disadvantage of exporting is that you then have a copy of your original - as a jpg / tif / psd - sitting on your hard drive.
True, but it's the only way to make the final image permanent.
You can overwrite
Which - if you do this for a TIFF/JPEG - will double your adjustments seen in LR and on the next export. Overwriting your originals by an export is NEVER a good idea.
Europe, Middle East and Africa