Project Selector is displayed is WBS order...
So if you really need an alphabetical order, just reorder your project in planning view

Good morning,

thank you for your answer, but my need is to be able to quickly find a project in the project selector, in order to select it, given the large number of projects in progress.

When you move the mouse over the project selector, you'll see a magnifying glass on its right.
Use ii to get a list of projects that can be sorted and filters, and then select your project (check button or double-click)
Note that this list accepts multi-selection (with CTRL or SHIFT)