When creating a window such as: window -Bfdop +Ld @name -1 -1 400 400, the window appears in the treebar, this is correct.
If you hide the window with /window -h @name and then bring it back with //window -ao @name, the window does not appear in the treebar.
I'm not sure if it's an issue, it's extremely unclear what switch can affect the window after creation.
Even passing back the all of the switches from the original /window to bring it back does not make it appear in the treebar, so I think it's a bug.

Thanks for your bug report. The reason for this is that the switches for /window were added over a very long time and each switch fulfilled a specific purpose at the time it was added. These behaviours cannot be changed now. /window -h permanently removes a window from the treebar. Newer switches were added later on, eg. -wN, that allow you to change where a window appears. You will need to use -wN for this purpose if you want to restore it to the treebar.

Alright, thanks.

I only reported it in case it was not correct, I will be using -w myself in this case