Settings on this options tab are saved automatically after each change.
Zooming can be controlled with CTRL-+ and CTRL-= shortcuts as well.
Note that tree and detail font sizing is relative to the main font size setting.
Left pane width is calculated from the percent of window size, if this is smaller than minimum width, then minimum width is used. If you want to have fixed width left pane, set minimum width to the desired width and set percent to 0.