When a mandatory field is filled with a space or a tab it is still shown in red as if it was empty.
Test case:
open Import Template window
create a new record
fill the Separator Character with a space
alternatively you can fill it with a tab, to fill a tab you can copy it from the clipboard
or to enter a tab you can use Ctrl+Shift+U then 9 then Space or Enter
the field is still shown as mandatory empty (red)
When a mandatory field is filled with a space or a tab it is still shown in red as if it was empty.
Test case:
open Import Template window
create a new record
fill the Separator Character with a space
alternatively you can fill it with a tab, to fill a tab you can copy it from the clipboard
or to enter a tab you can use Ctrl+Shift+U then 9 then Space or Enter
the field is still shown as mandatory empty (red)