You can change the default online store catalog title. This title is used as the tab title and for SEO.
Click Online Store > Commercial catalog > Category:
Select a section of the commercial catalog that is used in your online store > click Modify.
Go to the SEO tab > add the online store catalog title to the META TITLE template section. Click Save.
Then you'll see this title as the tab title:
Also, you can change the online store catalog's subcategories titles:
Or you can enable the auto-fill option for the online store catalog title:
