Use of "not NULL" in symbology

[JFBellemare]

This has been brought up in the forum before.

Create symbology using two (or more) attribute table fields, where (current and future) values are unknown, but have a default value set to NULL.
One example could be symbolizing the data this way:

"Null, Null" gets one symbol
"Null, Not Null" gets one symbol
"Not Null, Null" gets one symbol
"Not Null, Not Null" gets one symbol (this could simply be "all other values")

In addition to "not NULL", the general use of logical expressions could be handy.

[ColeAndrews]

EDIT: I would say this has been implemented.

[AlexanderGray]

I am also trying to do something similar.  I am able to get part of the way using an arcade expression as the field...  In my case I am trying to combine some values based on null or not null.  You can check if your field is null and concatenate some string to make a new value.  The problem I have is that I am not allowed to add new values to the list...  Add new values gives me "Requested operation could not be completed"  There are possible values that are not currently in the feature class but will some day be there.  I need to add my own classes to the symbol set from the options.

if ($feature.DATAHOST == null)
return concatenate( Text($feature.NBANDS), " none")
else
return concatenate( Text($feature.NBANDS), " host")