They publish the top 5 monthly to the ASX and the fund's...

They publish the top 5 monthly to the ASX and the fund's webpage. But only do a full report once a year. The current top 5 (hasn't really changed ever) are Alibaba, Alphabet, Facebook, Microsoft, Visa. Most recent monthly here: https://www.magellangroup.com.au/funds/magellan-high-conviction-trust-asx-mhh/reports-asx-releases/fund-updates/magellan-high-conviction-trust-asx-mhh-march-2020/

From a previous update (https://www.asx.com.au/asx/statistics/displayAnnouncement.do?display=pdf&idsId=02217670 ), they've also referenced stakes in SAP, Yum! Brands, LVMH, Estée Lauder, and Starbucks. That was some time in March, when they also reported around 19% of the fund in cash.
Quite possible this is the whole portfolio (fund guide is 8-12 companies), but could be something else in there.

https://www.magellangroup.com.au/funds/magellan-high-conviction-trust-asx-mhh/reports-asx-releases/
https://www.asx.com.au/asx/statistics/announcements.do?by=asxCode&asxCode=MHH&timeframe=D&period=M6