On Windows this change would be doable, but possibly messy since the font really should match in all the panes.  On Linux, the font size is determined by the GTK+ theme currently selected.  I can look into adding a setting, but, on Linux at least, changing the system theme should change the font in all widgets (except the editor) in Simply Fortran.

An option to set the typeface for the source files list in the Project pane.
(You'd also need to scale the folder and file icons in proportion to teh font size).

On at least one of my SF installations, it would be good if I could shrink this font a bit.
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John