For example, 未 and 末.
I tried looking for 同じ見える漢字 and 同見漢字 but they didn't seem to be correct or to refer to what I'm looking for.
Not exactly but 類字 is a close and established term for that and is found in dictionaries, although it doesn't exclude non-kanji writing systems. In practice, 類字 is mostly applied to kanji (and perhaps kana), like 同字 and 別字 are.
One word that I've seen used some is 類似【るいじ】漢字【かんじ】. Googling for this phrase in Japanese yields around 8.5K hits (adding "は" to the search string to filter specifically for Japanese). The second hit in that list (for me, anyway) is this page from a section of the SourceForge website, listing visually similar characters. For some reason the Machigai-Sagashi website in @Angelos's comment isn't loading for me, so apologies if this other site is a dupe or similar.