Is 7+ Taskbar Tweaker still running? Could it be that it's killed, maybe by an antivirus?

The reason for the incompatibility is that both 7+ Taskbar Tweaker and StartIsBack hook the same function, and one of the hooks takes over the other. I tried to revert the relevant portion of the changes from v5.11.3, please try beta v5.14.1.2 which I just released and let me know whether it solves the incompatibility.

You can get old versions of the tweaker here:

https://www.dropbox.com/sh/mcbychsh0xc1dvu/AAC7NwQTQ-tOTNL2BUZ_CwUua?dl=0

You can configure middle click to minimize the window. 

There was a problem calling GetProcAddress. Generally that shouldn't happen, but I remember seeing this issue when 7+ Taskbar Tweaker was running in compatibility mode. Please make sure that all compatibility options are off. If no compatibility options are enabled, my next guess would be a conflict with another program, such as another customization tool or your antivirus.

Yes, it's called win7appid as it was created for Windows 7 back when there was no Windows 10, but it's relevant for all Windows versions not older than Win7.

That's not possible with 7+ Taskbar Tweaker. As a workaround, you can try creating a custom shortcut with the win7appid tool and configure that AppID in the tweaker.

Sounds like the disable_topmost advanced option gets disabled when mIRC is maximized. I might look at it one day, but it sounds rather specific so it's not a priority.

What do you mean by "stops functioning"? Please provide more details and exact steps to reproduce the problem. If you can share a video that demonstrates it, that will help.

The virtual_desktop_order_fix option is implemented as following:

Internally, the taskbar items are kept in an ordered list in the taskbar code. Items are appended to the end of the list as they're added to the taskbar, but they're not re-ordered in the list when they're re-ordered on the taskbar. So, for example, if I open:

Notepad, Chrome, Firefox.

I can re-order them as much as I want, but if I switch to a different virtual desktop, and then switch back, I'll get them back as Notepad, Chrome, Firefox, since they're re-created from that list.

The virtual_desktop_order_fix option monitor for reorder events, and re-orders the list accordingly. As a result, when switching back to a virtual desktop, the taskbar buttons are re-created in the desired order.

Now, I'm not sure what exactly happens in the RDP scenario, but it looks like it requires a different, additional fix/workaround.

I'm not sure why a second virtual desktop interferes with your workflow, but I think that you don't need to actually keep it, all you need to do is to create a new one, switch to it, and destroy it right away. Or, in hotkeys: Win+Ctrl+D, Win+Ctrl+F4.