How do you change the default responsive sizes in Captivate 2017?

There may be other ways to do this but this is what I would recommend.

1. Close any running copies of Adobe Captivate.
2. Navigate to your Adobe Captivate 2017 x86 folder.
3. Copy a file called DeviceList.XML to somewhere else on your drive in case you need to restore it.
4. Edit the file located in the original location using a text editor such as Notepad.
5. Find all the entries that include candelete="0" and replace them with candelete="1"
6. Save the file to a location where you have permissions to do so (Desktop works fine)
7. Copy and paste the edited file over top of the file in the original location and grant permission to overwrite the original if necessary.
8. Open Captivate with Responsive design and delete and add any preview entries you wish.