PB 572 b1 x64 / Windows 7 x64 SP1 classic design
IDE: The formdesigner's toolbox is closed when you change the formdesigner's window style.
The toolbox window will not open again.
The only way to reopen the toolbox is to open a new form and then close the new form tab. That's a little awkwardly solved. In general, I miss a function to (re-)open the toolbox window, because you can close this window manually.
<Edit 02. Feb. 2020> Correction:
I take back the red marked sentences up there. The Toolbox window can be opened via the tools menu or with the hotkey ALT+V.
</Edit 02. Feb. 2020>
See the following animation:
Greetings
Kurzer