trill , triplets notes

The Handbook is your friend. :-)

https://handbook.musescore.org/notation/expressive-markings/ornaments
https://handbook.musescore.org/notation/rhythm-meter-and-measures/tuple…

I recommend that every new (or "new-ish" :-) user take an hour or two and simply read the entire Handbook (https://handbook.musescore.org/). Don't try to memorize it! Just skim through it and familiarize yourself with the contents! But read it all!!! Then you'll have an idea where to find things when issues come up in the future. "Didn't I see something about that in the Handbook?"

Welcome aboard and best of luck!!!