I'd like to just leave everything out when I'm done painting.
I wish I could leave all my paint materials as they are when I'm finished painting, instead of having to put everything away each time.
ーI'd like to just leave everything out when I'm done painting.
「絵を描き終えたら、全部出しっぱなしにしておきたい」
to leave ... out で「…を出したままにする」
when I'm done painting で「絵を描き終えたら」
ーI wish I could leave all my paint materials as they are when I'm finished painting, instead of having to put everything away each time.
「絵を描き終えたら、毎回全部片付ける代わりに、絵の具の道具を全部そのまま出しっぱなしにできたらなあ」
to leave all my paint materials as they are で「絵の具の道具全部をそのまま出しておく」instead of having to put everything away each time で「毎回全部片付ける代わりに」
ご参考まで!