I was trying to add
preloadtitle= to the docs. It's explained and works as part of the URL at Manual:Creating pages with preloaded text#Loading the preload file, e.g. https://www.mediawiki.org/w/wiki.phtml?title=Project:Sandbox&action=edit§ion=new&preloadtitle=New_Header - but it doesn't seem to be working properly as part of the inputbox...
Can anyone explain what I'm doing wrong?
<inputbox> type=comment preloadtitle=Log default=Project:Sandbox </inputbox>