Fastled fading only the lit leds

Is there a built-in function to FastLED that will fade the LEDs that are lit without having to manually store which led is lit or which intensity it is at?

void CFastLED::setBrightness ( uint8_t *scale* )

Set the global brightness scaling.
Parameters
scale a 0-255 value for how much to scale all leds before writing them out

Unless you mean individual LEDs.

Yes, I mean individual LEDs maybe half the strip or 1 third of the strip it could be any number of them.

are the other LEDs off and you only want to dimm those which are on or do you want to selectively dimm some of those that are lit?

The LED status is always stored anyway. It has to be - because the LED strip itself is write-only, you can't read pixel status.

The answer to your question, as I understand the replies so far, is "no". But if you post your code and explain what you need to do, maybe someone can help.

Basically, you would need to design a custom sequence, or a custom interface to some sequence code, to implement this feature.

Also, what is wrong with fading pixels that are off? - they would just remain off.

And... Fastled is fully documented. If you don't find a function like this in the library documentation, it doesn't exist.