The bracket layer trick for spacing and kerning

Hi! I’m wondering if there’s a way to get the bracket trick but with spacing/kerning values switch instead of switching shapes?

It’s for a font that uses different spacing “strategies” for big and small sizes, and intermediate steps don’t look that good, so I’d rather switched them at some point. I wonder if it can be done with features and conditions?

For spacing it might be easier with brace layers. Add one in the middle, re-interpolate it and then set the spacing you like.

Thank you! I guess that should work for static files without problems, but can it be done without storing paths in those intermediate layers/masters to keep the variable file smaller?

Undinge brace layers will be much smaller than bracket layers. And if you put a layer in the middle and re-interpolate it, it should not add much data.

If you want convenient separation of kerning, use the alternate glyph approach. Because then you have two different glyphs.