Hot to make thinner letters - font created in another software

Dear Glyphs community, I am new to this program and I have a very simple question. I have created a modular font with FontStruct but that software only allows a limited range of weights. I need to use a feature like the outline in Illustrator so I can make the letters thinner. I tried using the Offset Curve filter but that only seems to make the letters thicker. Can you please guide me through this?

Please help a beginner!


Have you tried Offset Curve with a negative offset value?

Thanks a lot for your quick reply! I am printing the Glyphs Handbook but I’m sure will come back with more questions soon!