Enable the "Show Global Search Configuration" menu.

We can configure object for global search from here.

Select object/model, name field, model fields. For one to many fields, you can configure from the smart button.

After that one wizard open, add one to many fields.

You can search the object based on configuration. "Global Search" visible to the whole odoo user.

Object wise search result looks like below.

On the click search result, it will redirect to that record.

Related record on click search result redirects on the new tab.

If multi-company activates in users look like this.

The multi-company result looks like below.

We can search by message, subject, or any content.

The searched result looks like this.

Tick the "Enable Menu Global Search" for search menus and redirect there.

The searched result.

Enter letter number to search after that letter in search box.

The searched result.

You can clear the search value using the cancel button and when clicked in the body it clears the search value.