no search icon on main toolbar of notebook 4.1.0b1 ?

I don't find any search (or search and replace) icon in Notebook 4.1.0b1 beta (on windows7).

Is it normal or a problem of my pc ?

It would look very odd / bad GUI for Windows users, who are using Office suites every day, if they don't see it.

Start by reproducing the missing search or search-and-replace icon in the main toolbar with Notebook 4.1.0b1 on Windows 7. Inspect the toolbar entry point and determine whether the controls are intentionally absent or missing; done means establishing the expected toolbar behavior and verifying it after the change.

Written by the indexing model from the issue text.