Lazpaint and .pdn files

[Tim]

Hi all.
Just downloaded Lazpaint as it opens .pdn files and I couldn't get a version of Paint.net to work on my W7 machine.

Just a couple of questions/issues:

1) Although Lazpaint opens my .pdn files, and seems to work fine with all the layers and stuff, how can I save as .pdn please?

1a) If I subsequently upgrade my machine to W10, and do manage to get Paint.net working, will it open lazpaint files?

2) Thumbnails of .pdn files are not showing. How can I get these please?

Thanks
Tim