How to concat a string value with ${currentUser()}" in task list filter

Hi everyone, I wanna add something like below into act_ru_filter at query column, but camunda omit first claim inserted:
{
“processVariables”: [
{
“name”: “unread-by-”+"${currentUser()}",
“value”: “unread-by-”+"${currentUser()}",
“operator”: “EQUALS”
}
],
“orQueries”: [
{
“includeAssignedTasks”: true,
“taskCandidateUserExpression”: “${currentUser()}”,
“taskAssigneeExpression”: “${currentUser()}”,
“taskCandidateGroupInExpression”: “${currentUserGroups()}”
}
]
}

this is my design an I need it as soon as possible, please help me