This page has a listing of how different alphabets and accented characters are sent with morse including Russian, Greek, Hebrew, Arabic, Japanese and Korean. I feel an overwhelming urge to change it from its dots and dashes layout to a didah format to reinforce the sound and not the visual structure of the characters. As comprehensive as these charts are, I’m still a little in the dark about some accents used in Portuguese. It could be that they’re simply not used in morse. Maybe listening to QSOs is the only way to confirm this.
Even the listing on the Portuguese Wikipedia page is missing the ã character. And this Brazilian page makes no mention of accented characters, even though it does explain that the codes for each character reflect their frequency in English.