Libreoffice starts with windows almost invisible

It’s possible to hunt down all of the confingurations or setup Xdefaults but, …
For a more generic alternative, there is a script that will adjust all window sizes within a workspace reference in another forum thread:
(Tips and Tricks - #12 by 1of7)
For example, this will cascade all windows if the command line option ‘cascade’ is selected.
If the script is placed in /usr/local/bin then creating a keybinding Alt-Esc using the command ‘/usr/local/bin/winfuncs.sh cascade’ will cascade (omit quotes) all windows in the workspace by hitting Alt-Esc.
Windows can be cascaded, tiled, etc.
Window placement and offsets are all accessible.
Works with xfce, KDE, fwm, gnome, …
Requires xorg, will not work in wayland.