I have found a two-part bug with the current Scrivener for Mac 3.5.2 (17487) running on a 2025 M4 iMac with the most-current macOS Sequoia 15.7.3 (24G419):
Part 1 - First, the side-arrow on the far right of the Title & Synopsis line in Outliner view is no longer visible, and right-clicking the bar only lists existing column names for you to switch on / off in this view (and there is no longer a ‘custom columns’ selection at the bottom of the list to create new entries).
However, this side arrow is still visible on my older MacBook Pro running macOS Monterey 12.7.6 (21H1320) with the same, current version of Scrivener 3.5.2 (this laptop has an Intel CPU from 2016, so Monterey was the last OS available for it).
Part 2 - Back on my M4 iMac, I can still navigate to Project | Project Settings… to create new Custom Metadata entries (for adding new columns), which works fine, but I noticed the Alignment assignment is incorrect. As a test, I created two new text entries and aligned them to ‘Center’, but they visually aligned to the right in the Outliner view. I had to assign their Alignment to ‘Right’ and then they visually aligned to the center, as expected.
My older MacBook Pro running Monterey correctly shows both their Center alignment assignment and are visually aligned to the center.
NOTE: I have not installed macOS Tahoe, so I don’t know if this bug exists there, but I currently don’t wish to update this iMac to that OS due to the ugly liquid glass / cluttered UI they’ve introduced. It would be nice to see if this can be fixed for Sequoia macOS users - thank you!