Setting "nvim-qt" fonts to "system fonts"

Hello,

Configuration:
Debian 11 (Bullseye), KDE
neovim-qt package version 0.2.16-1 (stable)
nvim-qt version v0.4.4

How does one set the “nvim-qt” “GuiFont” variable to use the “system font” in Debian Bullseye KDE?
I can set “GuiFont” to a specific font: “GuiFont DejaVu Sans Mono:h12”;
but I’m unable to set it to the system font: "GuiFont "?

How does one set the “nvim-qt” “Context Menu” font (mouse popup) to use the “system font”?

Thank you.