What phonetic shorthands (like 〼, 〆) are there in Japanese?

Question

I recently learned that the symbol 〼, called 枡記号【ますきごう】, can be used as a phonetic shorthand for ます, as in 豆腐あり[〼]【ます】. In a similar vein, I am aware that 〆 is used as a shorthand for しめ in 〆切【しめきり】 = 締め切り, and sometimes in other words.

What other phonetic shorthands should a reader of Japanese be aware of? (Or, is there a word I can use to describe all of these things so I can look them up myself? 記号 is too broad, since it includes all kinds of symbols, and I don't know of any more specific word.) For the purposes of this question, let us ignore 略字, which I'm led to understand are fairly numerous.

If there are a lot of them, feel free to close as "too broad", but I imagine there can't be that many of them.

Answer 1

「々」, or 同{どう}の字点{じてん} (dōnojiten), indicates the repetition of the previous kanji. For example, 「人々」, used instead of 「人人」, is read as hitobito.

In terms of hiragana, the symbol 「ゝ」is used. It's mostly used in names, such as 「おゝの」(Ōno) and 「いすゞ」(Isuzu). Katakana uses a different symbol, 「ヽ」, but is used in the same way as its hiragana counterpart. While widespread in old Japanese texts, the kana iteration marks are generally not used in modern Japanese outside proper names, though they may appear in informal handwritten texts.

To repeat multiple characters, the character 「〱」(くの字点, kunojiten) is used. Note the difference between the hiragana 「く」and 「〱」- you should be able to tell the difference based on context. Vertical writing makes the difference clearer. Kunojiten stretch to fill the space typically occupied by two characters, but may indicate a repetition of more than two characters - they indicate that the preceding word or phrase be repeated. For example, 「何とした〱」is read as 「何とした何とした」。As support for these is limited, the ordinary forward slash "／" and backward slash "＼" are occasionally used as substitutes.

You can read more here.

Answer 2

The subset of 約物（特殊記号）you are referring to is 準{じゅん}仮名・漢字. One common symbol you will see in this category is 々. It has various names but denotes a repetition of kanji.

E.g. 各々{おのおの} or 時々{ときどき}.