Hi Ian
Thanks for posting in the Community!
I'm not sure what you mean exactly by "flipping a symbol vertically and horizontally". It is possible to rotate a shape clicking the double-sided arrow located right next to any selected shape you have dragged onto your canvas and dragging it in the desired direction:

Here I rotated the shape to the right:

If you double click the text on your shape the entire content will be selected and will be highlighted in blue:

If you hit the delete key then the entirety of the text will be deleted.
However if you click once more a text cursor will allow you to have a more granular control over what you would like to remove (delete specific letters or chunks of text):

I hope this helps! Let us know if you have any questions!