Hi. The top of the page “search field” in asana is one of the most practical features imho and one that I use all the time, maybe up to 100 times per day.
In focussed task view, regrettably, currently, the search field disappears. I think it would be a great idea to keep it. Unlike the big long left menu and the list of tasks in the project, that should be hidden to allow to focus on one task, the search field is only one line on the top of the page and is very practical