Create a polygon

Select the label in the left panel
Click on the button
Draw your polygon
Press Escape

Create a multipolygon

Create a polygon as explained above
Select this polygon (by double-clicking on it)
Click on the button
Draw your polygon
Press Escape

Delete a polygon

Press Ctrl and click on the polygon

Change image

Click on previous or next arrows or use the list or random button

Change label of an existing polygon

Select your polygon
Select the desired label
Press Escape

Export to Coco

Go to the admin section
Click on "Generate Masks"
Once mask generation is completed, click on one of the two download buttons