User blog comment:MisterWoodhouse/The first migrations to the Unified Community Platform/@comment-26939652-20200827110929

It's extremely hard on the UCP to get to source editor for an infobox, even if source editor is your default. Takes 3 hoops to jump through. Even more for a new infobox.

Saving in source editor for an infobox does nothing.

Did you even test this? You cannot migrate user platforms with infoboxes this way.

Example: https://wreckit-woodhouse.fandom.com/wiki/Template:Infobox_user?action=edit&useeditor=source&templateType=infobox

When I click save, some modal pops up for a split second that I can't read so short, no network traffic at all, no exceptions, no console logs.