I have this to open a new window in one of my scripts, where $Browser is declared above:
Start-Process $Browser ('--new-window', '--start-maximized', 'about:blank') -ErrorVariable Test
Then to open more tabs in that same window, I use this, where $URL is pulled from an array:
Start-Process $Browser $URL -ErrorVariable Test
NOTE: This works with Edge, Chrome and Firefox. It does not work with IE. IE requires COM-Object coding to open tabs in the new window you opened in the first line. Otherwise the URLs you expect to be in new tabs all open in new windows.
