MongoDB Compass: Cannot find index to verify that join fields will be unique

I'm trying to $merge documents from Read-Only View (aka ROV) into On-Demand Materialized View (aka OMV). With Compass for now. I've created a pipeline in Aggregations section of Compass:

[{
    $project: {
        _id: 0,
        RunDate: 1,
        Manufacturer: 1,
        Name: 1,
        Workgroup: 1,
        TotalPhysicalMemory: 1,
        Model: 1,
        PartOfDomain: 1,
        Domain: 1,
        NumberOfLogicalProcessors: 1
    }
}, {
    $merge: {
        into: 'omv_WSCReportIndex',
        on: 'Name',
        whenMatched: 'replace',
        whenNotMatched: 'insert'
    }
}]

Basically I want OMV with unique 'Name' field where I will be inserting computer docs like this one (and overwriting ones, if needed):

RunDate: "2022-08-23 10:54:38Z"
Manufacturer: "VMware, Inc."
Name: "SRV010"
Workgroup: null
TotalPhysicalMemory: 16
Model: "VMware7,1"
PartOfDomain: true
Domain: "test.loc"
NumberOfLogicalProcessors: 4

Problem is I'm getting an error when I click RUN: Cannot find index to verify that join fields will be unique. I've tried creating index on 'omv_WSCReportIndex' for 'Name' field like "1-Type Index with Unique", "Text-Type Index with Unique", tried to create index with Collation object..

I can't just figure it out how to make this OMV. Please help!