drag then drop the first Panel to where you drag it.
sometimes the DnD proxy(the dotted line box) will missing.
if this happened, drag the panel to the left top of second panel(title: Google tools), the DnD proxy will appear.
test with ZK9.1.0 on Edge/Firefox
can't drop the first panel to where you drag it from(since the dragging position miscalculated)
- try to drag to the frist portalChildren but the DnD proxy is weird
2. move the mouse to the left top, the DnD proxy position is working properly.
can drop the first panel to where you drag it from, and the DnD proxy is working properly according to the mouse position.
Edge/Firefox sometimes happened in the frist drag, other browsers happened since second drag mostly.