I am reading about the RMT peripheral library and thinking if it would be possible to use it for raw receive and re-transmit of an unknown bit stream . In RMT examples (\esp-idf-v5.0\examples\peripherals\rmt\ musical_buzzer ) there is a "musical buzzer" which kind of does a similar task already, but...

It takes time for Eclipse to index all those files. Just leave it running for a couple of minutes and it will fix itself!