Unclassed Colors ArcGIS Pro: Adding a value marker in the legend

[HannahHyatt]

I have an idea to add a feature into the Unclassed Colors symbology option. I find that for some forms of data representation the classification methods can mask what's really going on. Sometimes, they are spot on, but others it's best to just see the range of values across a map. 

In cases such as these, I still want the map reader to be able to orient themselves to what the varying colors on the color ramp are indicating. Obviously, the Unclassed Colors legend already gives the highest and lowest values. I would like to be able to add a mark/arrow on the legend which helps the map viewer orient themselves to what value those middle gradient colors represent. 

It appears that you can do something like this in AGOL, however, it would be ideal to have a similar option in ArcGIS Pro. Not only would it be helpful to have something like a middle marker that would tell you the value that underlies that mark, but it would be nice to be able to choose where that mark falls. For example, if the data set is skewed right, it would be nice to be able to place the third mark close to where the data starts to get "exciting". 

To my knowledge, there is no way to do this accurately. Currently I've tried a work around where I create my legend in another platform (PowerPoint) and take a best guess at the middle of the color ramp. Obviously, this is far from the best way to do this.