Google has rolled out the new, more compact, menu bar for Google Merchant Center Next. This was part of a slew of user interface updates that Google has been slowly rolling out for Merchant Center Next over the past several months.
Brodie Clark posted about this on X and wrote:
Looks like GMC Next has now transferred completely to the new menu layout for all accounts. This has been a phased rollout for a while and looks like they've finally made the switch. There has been quite a few bugs in GMC lately so this is potentially the reason.
Here is a screenshot:
Forum discussion at X.