What symbols are customarily used for “○○” in English?

What symbols are customarily used for “○○” in English?

As you point out, the asterisk is used in English as censorship: "He's a f* * * ing idiot! I hate the t * * t." (It is usual, but not necessary, to have as many asterisks as there are hidden letters.) (NB, there is no space between the asterisks - it is simply that the formatting uses asterisks for other purposes.)

The blank / underscore is used to hide an identity "Mr ______ from _____ made some comments about the French." (This is now old-fashioned.)

The blank / underscore is also used in questions as a place holder for an answer "I never _____(to see) the incident."

Square brackets with ellipsis are used to indicate missing and unimportant words "The law states that "Any person [...] who [...] drives sheep, [...] across the bridge must pay a toll of £1.00" This might represent "Any person being an adult who herds, moves, conducts or drives sheep, cows, geese, goats, horses across the bridge must pay a toll of £1.00"

I am not sure what you mean by "whatever word you like" is a valid description, e.g. "[.......] is rather large" will only work with a restricted number of words, rather than "any I might like".