This is not true! Start11 replaces the default taskbar in Windows by hiding the taskbar and implementing its own via the software. It's very possible for Stardock to include vertical taskbars in Start11 and is an absolute necessity for me.

I've had my start menu to the left side for a super long time and when I discovered Start11 I was super hopeful that they would have the option to move it to the left. However this turns out not to be the case as of right now 😞

It's only the beta so a lot more things will be added hopefully including vertical taskbars

For what it is worth, I, too, prefer the taskbar to be vertical and on the left side of my screen. If possible, and since it is being moved already, Start11 could also do vertical that would be a great feature. However since there was, or is, a registry hack to move it from the bottom to the top, Stardock might not be implementing their own, but rather exposing the capabilities already in Windows 11, but hidden.

In Windows 10 you can drag the taskbar to either side of the screen; no extra software, such as Start10, is necessary to do this.  As for a replacement taskbar and start menu perhaps you're thinking of NextStart which is part of Winstep?  OK, after a little research I think you're referring to StartAllBack, which addresses the limitations of the Windows 11 taskbar.  

I'm surprised at the number of you who want the taskbar to the left.  

It would be nice if Stardock would implement the same (or at least respond here) so that we would not need to choose between switching and losing the vertical menu.

Technically already possible... (I used this, it works, and I liked it, but bottom line I did switch back to Windows 11 Standard bar)

Winaero Tweaker has an option under its Windows 11 section for 'Classic Taskbar' to turn on the old Windows 10 style Taskbar...

Once that is enabled, you can then change taskbar location to the side...

Several things will be broken, there will be a few links on the 'Classic Taskbar' to fix about 80% of the problems...

The 'Win-x' menu was still broken by doing this, and most of the icons Microsoft puts in the system tray were broken in some way (Wifi Connect menu was blank for instance)

But bottom line worst problem is that it is currently known for sure that Microsoft will continue to invest into the current Windows 11 taskbar, but it is currently unknown if the classic taskbar will get fixed or get worse over time...  Will it get a Windows 11.1 that fixes the taskbar screw-ups like Win8 did? who knows...

I figured since I was going to have to help other people with Windows 11 on occasion I might as well figure it out and went back, though it is severely missed...

Quoting Chasbo,

reply 10

I'm surprised at the number of you who want the taskbar to the left.  

You really like wasting so much of your vertical space while having much more horizontal space? Try it once, you'll never go back. Also more space for each program window to appear (no need to group windows).

Anyway...

Start11 v1 was not intended to make much change to the taskbar.  It is about the menus, exposing some OS options for the taskbar and fixing the right click menu.

Start11 v1.1 is targeting taskbar features.

I'm still at Windows 10 using Start10 and planning to move into 11 soon (3 Gaming Rigs). I always used my Taskbar on the left side as well so I will only upgrade to Start11 if we have that feature implemented otherwise I will have to move into StartAllBack which is able to do that.

The thing is, StartAllBack allows moving the taskbar to the left and right, but I love the Windows 10 start menu that only Start11 provides. Unfortunately they don't play well together, so allowing to move the taskbar to be placed vertically would be much appreciated. Until then, I'll stick with StartAllBack because moving the taskbar is for me personally more important than having the tile-based Win 10 start menu.