Custom actions are not available in the Essentials solution.
If you need to archive/delete a Microsoft Teams group using a CoreView custom action, you can import the script below.
Custom action script:
{
"id": "45fca056-5c23-4728-a67f-096b270eb684",
"title": "Teams - Archive Teams group",
"description": "A custom action to archive a Teams group and set the SharePoint site read-only for Team members",
"lastModified": "2021-05-10T07:29:10.4510000Z",
"target": "Teams",
"tags": [],
"vars": [
{
"name": "Guid",
"type": "string",
"isRequired": false
}
],
"params": [
{
"name": "DisplayName",
"type": "string",
"isDefault": true
}
],
"columns": {
"DisplayName": ""
},
"version": 5,
"statement": "param ([string]$DisplayName, [string]$Guid)\r\n\r\nSet-TeamArchivedState -GroupId $Guid -Archived:$true -SetSpoSiteReadOnlyForMembers:$true"
}