How to limit exported commands from binary powershell module (*.dll file)?

I can't think of an environment variable-based solution, but if executing a command to make the "hidden" cmdlets visible is acceptable, you can take the following approach:

• Create a full-fledged, directory-based module around your cmdlet-containing *.dll, through whose module manifest (.psd1) you can limit what cmdlets are made available to the caller on import.

• If you want to (later or alternatively) load all cmdlets, run Import-Module -Force directly on the *.dll, which will import all cmdlets (all public Cmdlet and/or PSCmdlet-derived classes).

If you define helper function Import-AllCmdlets (source code below), you can force importing of all cmdlets as follows, assuming your module's name is Foo:

# -Verbose shows what cmdlets are imported.
Get-Module -ListAvailable Foo | Import-AllCmdlets -Verbose

Import-AllCmdlets source code:

function Import-AllCmdlets {
  param(
    [Parameter(ValueFromPipeline)]
    [psmoduleinfo] $module
  )
  process {
    if ($module.RootModule -notlike '*.dll') {
      Write-Error "Module $module has no binary root module."
      return
    }
    Import-Module -Force (Join-Path (Split-Path $module.Path) $module.RootModule)
  }
}