This plugin shows in a light orange colour the same glyph of another opened font. It can be useful for visual comparison of italics with normal styles,or different versions of the same font.
Open two fonts and activate the plugin via View>Show Next Font menu item. The ammount of masters of the fonts should be the same, in case of difference the plugin shows the first master only.
Under the right click menu you can find a menu item to swap next font view between outline and fill mode.
Also under the same menu you can sync edit views across open fonts via the "Sync edit views" item.
For better update handling install the plugin via the Window > Plugin Manager inside Glyphs App and restart the app.
This plugin was inspired by the Show Next Master plugin from Mark Frömberg (mirque.de).
If this plugin is helpful for you, maybe you can consider making a donation ;)