定数が入っていたり、さすがに分かりにくいので中間変数を用意しようと思います。

    val existsWhitespaces = charsBetweenTokens(prev, current) != 0
    val notExistsSingleLine = linesBetweenTokens(lines, prev, current) != 1
    ...
    isSingleColonToken(current, next) && existsWhitespaces && notExistsSingleLine
    ...
    isSingleColonToken(current, next) && existsWhitespaces
    
    val notExistsSingleWhitespace = charsBetweenTokens(current, next)  != 1
    val notExistsSingleLine = linesBetweenTokens(lines, current, next) != 1
    ...
    isSingleColonToken(current, next) && notExistsSingleWhitespace && notExistsSingleLine
    ...
    isSingleColonToken(current, next) && notExistsSingleWhitespace