This would be very useful for deliverables. We cannot use conditional statements in smart text but if you could this would be possible or something more natively. Long term, we would want these slopes to update dynamically with the text.
There is also no way to quickly apply a single slope indicator to a surface. You would have to do this with a block and manually adjust the block to align with the slope at this position. This would also be invalid if any changes were made to the surface at this spot.