Delete chapter: click on the 3 dots -> Archive/delete page
All the pages in the chapter will be deleted.
Remember that if the chapter and its pages have been published in a previous revision they will be archived when the revision is published. Otherwise, they will be deleted when saved.
Add import new chapter: click on Add chapter (which will be placed at the bottom) drag and drop the new chapter where you what it to be. Save.
Click on the new chapter and go to Settings -> Import.
Select "Import file as a new chapter"
Note: please remember to use Chrome when taking this action. If you want to know more about the performance please check our article Browser Compatibility.