My setup: Debian-9 stretch linux, I have installed PlayOnLinux via Synaptic Package Manager.
So now, to Install Blogdesk and BlogJet offline editors:
1) download BlogDesk: https://www.blogdesk.org/en/
download BlogDesk: https://www.blogjet.com/
2) Launch PlayOnLinux: since Blogdesk/BlogJet are not part of PlayOnLinux's default programs, they have to be installed/added manually.
3) with PlayOnLinux open, Click File >> Install >> click Install a non-listed program >>
BlogJet has been Installed. Same procedure applies to Blogdesk.