A genuine question.
We bought a Ryobi line trimmer (the "base" model $119) a week ago and tried twice. I thought this was the only model that can be used as an edger (I am a noob). Later after watching some YouTube, I realise basically any trimmer can be used as an edge trmmer if the user is not too picky.
I wanted to buy a more expensive Ryobi model ($249 iirc). I am wondering if it is possible to go back to Bunnings with a used trimmer and ask for upgrading it to a more expensive model.
I'm guessing no.
Sell your smaller trimmer on a local marketplace, cop the loss on the chin, and purchase the larger model.
Edging (not that sort jv) with a line trimmer can take a bit of technique trial and error.