Delete Button Missing in SharePoint Column? Here is How to Delete them.

How to delete a Column when Delete Buttonis missing:
Unable to delete list column in SharePoint since there is no delete button in field properties? In some cases, columns added through "Add existing columns" doesn't provide the option to delete! To make them deletable, just revert these two properties: AllowDeletion & Sealed

Here is how to delete SharePoint list column programmatically with PowerShell: 

#Get the Web
$web = Get-SPWeb "http://sharepoint.crescent.com/sites/pmo"

#Get the List
$list = $web.Lists["Design Documents"]

#Get the column
$column = $list.Fields["Category"]

#Disable Delete
$column.AllowDeletion = $true
$column.Sealed = $false
$column.Update()

#To delete a SharePoint list column in PowerShell, use: $column.Delete() 

$web.Dispose() 

We can also make fields to Sealed, So that nobody can change the field settings.

SharePoint Manager tool  can be used to set these properties. Just navigate to the site, list or library and set the "AllowDeletion" property to false, save the changes. This hides delete option in SharePoint list.

Here is my another post to make a column non-deletable: How to Prevent SharePoint List or Columns from Deletion