I've imported bookmarks from Firefox to Orion 0.99.131.0.1-beta on OS 15.3.1.
On my desktop, the Bookmarks Bar is set up as I like it, other bookmarks show up in the Bookmarks Menu.
I have set up iCloud sync for Orion, and made sure sync settings are exactly as described in your user manual. I've gone through and turned the sync settings off and back on, on every device. I've turned syncing for Orion off and back on in iCloud. I've rebooted all of my devices. Every setting is as it should be.
But still, my desktop bookmarks don't show up on any other device. If I can't get this working, then I can't use Orion.
I expect if settings are correct, then bookmarks will sync!
Version 0.99.131.0.1-beta (WebKit 621.1.2.111.4), macOS Sequoia 15.3.1 build 24D70
Sequoia (15)
18