Welcome to our community, Billb
You are able to export backgrounds via the Library panel. Try
clicking View > Show Library. With the Library visible, you are
able to right-click the image and choose "Export".
Note there is a Captivate way to "White out" an area of the
background. You click Insert > Highlight Box and configure it
for 0% transparency and the color white. Then position it over the
area you wish to white out. Now right-click the Highlight Box and
choose "Merge into Background". The net effect is identical to what
you would obtain by editing the background in something like
Photoshop or Gimp.
As for grabbing extra screens, sure! Just tap the Print
Screen key on your keyboard while you are recording. That action
will force Captivate to grab that screen.
Cheers... Rick