On all the headers you have the option to have a icon or search bar on desktop, that options is also available on mobile now:

Option - Search bar

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/85300e28-d2de-4930-965b-8181264cf4d5/Screen_Shot_2021-07-16_at_09.42.21.png

Option - Icon

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/a5fc4915-5b6c-4e4c-9dbe-3e7a562cfff1/Screen_Shot_2021-07-16_at_09.43.10.png