This is done through managed app config.
Chrome has a surprising amount of things that can be managed in this way. details of which are here:
https://chromeenterprise.google/policies/#ManagedBookmarks
It does go into some detail, so I'll give an example of some simple bookmarks
We'll create a new policy using Managed App Config for Android
We can add a new entry, find Managed Bookmarks in the list and add something like the following:
[{"toplevel_name": "Acme Bookmarks"}, { "name": "Cisco", "url": "cisco.com" }, { "name": "Meraki", "url": "meraki.com"}]