Concatenating strings is easy with Javascript and executescript_sandbox:
executescript_sandbox | return ${a} + ${b} | c
PS: For random number generation see Random Date of Birth generator - #2 by ulrich
Adding Strings Test macro:
{
"Name": "add strings",
"CreationDate": "2021-3-31",
"Commands": [
{
"Command": "store",
"Target": "12345678",
"Value": "a"
},
{
"Command": "store",
"Target": "@gmail.com",
"Value": "b"
},
{
"Command": "executeScript_Sandbox",
"Target": "return ${a} + ${b}",
"Value": "c"
},
{
"Command": "echo",
"Target": "c = ${c}",
"Value": "blue"
}
]
}