If you made it through the title of this post, you're in the right place. Due to security restrictions on a Windows 10 machine I was using, I needed to run a group of PowerShell commands in a single command from a batch file, and I found the solution here:
https://dmitrysotnikov.wordpress.com/2008/06/27/powershell-script-in-a-bat-file/
Basically, you enclose the whole set of commands in curly braces, encode those to a Base64 string, then pass that encoded string to the PowerShell command with the -EncodedCommand parameter. This encoded string is the "pseudo here file" mentioned in the title.
I needed the same code run every time, so the manual step of copy-and-pasting the encoded string wasn't a problem for me. If you need to programattically modify the code that needs to run, you're on your own.