Can't reach certain configurations

[dirkgr]

I have this configuration:

There is no way to reach this configuration:

[Riateche]

I suspect that it can be caused by restoring a configuration from an older revision. I added 'Clear state' action to the main menu. Try to clear state and reproduce the same error. If it can be reproduced, describe the order of your actions.

[dirkgr]

I commented out the initial call to on_actionRestoreState_triggered(), and it starts with two columns, [1, 2, 3] on the left, and [4, 5, 6] on the right.

1. I drag [4, 5, 6] to the left, so that all windows are in one tab view.
2. I drag 3 underneath all of them, so that [1, 2, 4, 5, 6] are in the top half, and [3] is in the bottom half.
3. I try to drag 4 next to 3, so that [1, 2, 4, 6] are in the top half, and the bottom half is split vertically, with [3] on the left and [4] on the right. I can't do that.

Does that help? I can take screenshots, if you like.