When discs form around stars, there is interaction of angular momentum between disc, planets and parent star, and this interaction affects the rotation of the parent star, and that will affect the lithium abundance.

There are many unidentified bands in the spectra of stars. Wide bands are produced by some complex molecules in the interstellar space.

Let me mention that not all sun-like stars host planets - perhaps about 30% of them are planet-builders. It's not so easy to form a planet!

If you see, in the spectrum of a planet host star, strange chemical elements, it can be a signal from a civilization which is there.