Maybe I am wrong, but do I recall that this was actually an option in the past? or am i dreaming… however, this would be useful. could be in the top left corner of the info panel 
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That was never there. I don’t like the checkbox as it uses to much space. (the names can be really long for some scripts…).
But I though about adding some indicator for not exporting glyphs.
I’m not so sure about this. Is an export option something you check/uncheck all the time? I think this check box will give you more accidents than ease.
I think an indicator would be useful, I’m doing a typeface now that uses a lot of components and am often flipping back to the Font tab to check whether this glyph is one I’ve decided to use on export or not.
I have a plugin that adds enable/disable export to the context menu. I’ll publish it in a few days.