How can I add a new XML DataSource from PowerShell?

I am trying to import an XML datasource using powershell. From reading the docs (https://help.remotedesktopmanager.com/index.html?new-rdmdatasource.htm), it seems like I should be able to do:

C:\> Import-Module -Name "${env:ProgramFiles(x86)}\Devolutions\Remote Desktop Manager\RemoteDesktopManager.PowerShellModule.psd1"
C:\> $s = New-RDMDataSource -XML -FileName c:\path\to\test1.xml -Name test1
C:\> Set-RDMDataSource -DataSource $s


This doesn't have an output or indicate any errors, but it also doesn't work.

It looks like the output from New-RDMDataSource is ok:

C:\> $s

ID Name Type
-- ---- ----
0e773a8c-0483-4a61-a797-3a226d62dffd test1 Xml


However, after using Set-RDMDataSource (even if I use Update-RDMUI or restart RDM), this new entry doesn't show up in the UI or the output of Get-RDMDataSource.

I also tried this with the -SetDatasource, with no success.

How do I add a new XML datasource from powershell? (Or just automate it, somehow)