Hey there.

The following exists now since quite a while (a year?) and I've always
just been too lazy to report O:-)

When I start plain libreoffice, I see some white program icon in
e.g. Cinanmon’s window list, same if then I star a new spreadsheet.

But when I save that, close libreoffice and do e.g.
$ libreoffice foo.ods

The window has no longer an icon (at all) in the window list
(it does though have one in the pop-up from the workspace-swichter,
usually Alt-Tab).

And I see this only with Libreoffice, no other programs.

Turns out a fix is the following:
$ cp /usr/share/applications/libreoffice-calc.desktop ~/.local/share/applications/
and in the copied file change the line:
  StartupWMClass=libreoffice-calc
to
  StartupWMClass=soffice



Thanks,
Chris.