Save-CMSoftwareUpdate has no option to select the download source
The Admin-Console is capable to download Softwareupdates from WSUS or a Networkshare wsuscontent). But there ist no commandlet for that. Save-CMSoftwareUpdate seems to be the commandlet for that. If so, than the parameters for the source are missing.
Updating title to reflect the request here
On the Download Location of the Download Software Updates Wizard you have the option to Download from the internet or Download from a location on my network. I believe this is what's missing with the CMDlet. The current Location parameter is written as a location to download to vs download from.
I believe this is referring to the scenario where you don't want to download updates from the internet but instead from a location such as WSUSContent.
Save-CMSoftwareUpdate is the cmdlet that is meant to accomplish this scenario. You can use -Location to specify the download location.
Can you elaborate on the workflow in the administrator console that you cannot complete with Save-CMSoftwareUpdate?