Function vcopyq_laneq_s8 

pub fn vcopyq_laneq_s8(
    a: int8x16_t,
    const LANE1: i32,
    b: int8x16_t,
    const LANE2: i32,
) -> int8x16_t

Available on (AArch64 or ARM64EC) and target feature neon only.

Insert vector element from another vector element Arm’s documentation