The ability to move and resize the Taskbar, as well as customize the size and layout of the Start menu should begin rolling out imminently, if the latest Windows 11 preview builds are anything to go by.

Earlier this year, Microsoft announced big updates for the Start menu and Taskbar on Windows 11 that would address users biggest complaints and bring highly requested features and functionality to the OS. Those changes include the ability to move and resize the Taskbar, as well as customize the size and different sections that appear within the Start menu.
Those features have been in public preview ever since, but those outside of the Windows Insider Program are yet to experience these new features. Now however, Microsoft has confirmed that it's now gearing up to ship the updated Taskbar and Start menu to everyone next month, as the features are now in the final Windows Preview Channel before public rollout.
As of yesterday, the movable and resizable Taskbar, along with the customizable Start menu, and other polish and quality of life improvements, made their way to the Windows 11 Release Preview Channel. This is the last stop before features begin shipping in public, non-Insider updates.

Usually, when a feature lands in the Release Preview Channel, it's no more than two or three weeks away from appearing in a public update. Usually, that's with the non-security feature preview update that drops at the end of every month, followed by the security-focused Patch Tuesday which is released on the second Tuesday of every month.
That means if everything goes according to plan, the new Taskbar and Start menu updates will begin rolling out later this month for users with the "Get the latest updates as soon as they're available" toggle in Windows Update switched on, and next month for everyone else.