The view windows are just that, separate windows. AC3D is set up so you don't need to click on each view to start working in it. I think an old version (i.e. very old, possibly Motif UI?) required clicking and it got in the way of the workflow and was unpopular.
You could try this:
Edit tcl/ac3d.tcl
Look for this function
Code:
"proc setting_edit { parent var { text "" } { balloon "" } { width ""} } {"
After this line:
Code:
entry $f.le$var -textvariable $var
add this line:
Code:
bind $f.le$var <Return> {focus .}
Save the file and restart AC3D.
This addition will cause the focus to leave an entry-field when enter/return is pressed in that field. This will work for the move-to/Size-to/Move/Scale UIs on the control panel but could be added to other fields if you think it would be useful.