I get and have been getting full thumbnails for all CorelDRAW and Photo-PAINT files in Windows 10.

Krishna5907 said:

Oberon Thumbnailer for CorelDRAW/Corel DESIGNER is excellent for Thumbnail. But Could not be able to use it in 2019. Can Anyone Update the Macro code to use it in 2018 or 2019.

You could look at this page on the MemorialDESIGNER web site.

They have a link there for an updated version of Thumbnailer. I do not have much personal experience with it, but it's something you could try.