Is it possible to switch between background to foreground, and keep the fill on, I’d like to do this to compare back and forth, thanks.
I am not sure I understand what you mean. Put the cursor to the left of the glyph in question and press cmd-B while in text mode (T). Fill will be preserved unless you have a different setting in View > Fill Preview. You can type several instances of the letter next to each other, Background will only be shown for the current one. This way you can have back- and foreground side by side.
Thanks, that should do it!