[Usability]Unique control panels

[Gregory Merchan <merchan phys lsu edu>]

I noticed two bug reports today for control panels which can be shown twice
but fail to display the same information. (#98079, #98085)

Control panels should not allow multiple simultaneous instances.
Instead, later invocations should cause a running instance to be shown.

More than one instance could confuse users and does not provide useful
information.


Cheers,
Greg Merchan