You can look up limits in the Maximum Values list, which nowadays is interactive:

https://docs.fortinet.com/max-value-table

For example, a VM0 has a max. number of interfaces of 4K, and a max. no. of IPsec tunnels of 2000.
For This case , a MSL has a max. number of interfaces of 16K, and a max. no. of IPsec tunnels of 40K

Depending on your VM resources, you might exhaust your cpu/ram/bandwidth way before maxing out the total number of allowed ipsec tunnels.

config user local
    edit "<user1_name>"
        set type password
        set passwd <user1_pwd>
    next
	edit "<user2_name>"
        set type password
        set passwd <user2_pwd>
    next
	.
	.
	.
end

config user group
    edit "SSL_VPN_GROUP"
        set member "<user1_name>,<user2_name>......."
    next
end

import re

def write_user(file_path, pair_list) -> None:
    """
    写入配置文件。
    Args:
      file_path: 配置文件路径
      pair_list: 用户密码列表
    """

    with open(file_path, "w") as f:
        f.write("config user local\n")
        for pair in pair_list:
            f.write("    edit \"{}""\"\n".format(pair['username']))
            f.write("        set type password\n")
            f.write("        set passwd {}\n".format(pair['password']))
            f.write("    next\n")
        f.write("end\n")


def write_user_group(file_path, pair_list) -> None:
    """
    写入配置文件。
    Args:
      file_path: 配置文件路径
      pair_list: 用户密码列表
    """
    with open(file_path, "a") as f:
        f.write("\nconfig user local\n")
        f.write("    edit \"SSL_VPN_GROUP\"\n")
        f.write("        set member ")
        f.write("\"")
        for i, pair in enumerate(pair_list):
            f.write("{}".format(pair['username']))
            if i != len(pair_list) - 1:
                f.write(",")
        f.write("\"")
        f.write("\n    next\n")
        f.write("end\n")


def format_users(data_source_path) -> list:
    """
    Reads a text file and formats each line in the following pattern:

    "username {password}"

    Args:
      data_source_path: The path to the origin data.

    Returns:
      username password KV list
    """

    with open(data_source_path, "r") as f:
        pattern = r"\s+|,|;"  # 过滤其中的空格、逗号和分号
        result = []
        for line in f:
            pair_map = {}
            match = re.match(r"^(.+)+([\s*,;])+(.+)$", line)  # 两边是任意长度的字符串，中间是任意个空格 逗号或者分号
            print("match", match)
            if match:
                pair_map['username'] = re.sub(pattern, "", str(match.groups()[0]))
                pair_map['password'] = re.sub(pattern, "", str(match.groups()[1]))
                result.append(pair_map)
        print("result length: ", len(result))

    return result


if __name__ == "__main__":
    read_path = "origin.txt"
    res = format_users(read_path)
    write_path = "result.txt"
    write_user(write_path, res)
    write_user_group(write_path, res)

# origin.txt
sunway1, 123456
sunway2, 123456
sunway3, 123456
sunway4, 123456
sunway5, 123456