There is no way to set the default zoom level

[Azercoco]

Because there is no zoom level slider in the appearance tab, the zoom level is reset at each restart which is not pleasant for high DPI screen.

[maltejur]

This may not be the most ergonomic option, but you can set the zoom level through the QT_SCALE_FACTOR environment variable. So for example start it with QT_SCALE_FACTOR=2 discord-screenaudio or set that environment variable permanently in your desktop file.