maximebrun Native "Select clips after/before playhead" is faster indeed, because it uses some internal code.
"Select clips after/before playhead" inside Excalibur uses API. Previously I was running code to select all clips one by one, now I use mix of setting in/out point and then running native Premiere command "Select clips inside in/out".
However this native command does the same approach as I used before: selecting clips one by one.