I've been following the improvements made to symbolic creation closely in AGOL and appreciate the advancements that have been made so far, but I'd like to see a few more capabilities added to further enhance the OOB cartographic capabilities.
In recent releases the capabilities to manage stacked vector symbols has been added, which is great. The main piece that is missing from the UI (and my idea) is to include an "add symbol" tool to allow a user to further modify or create custom symbols.
Example 1: In this point symbol example I'd like to swap the circle background to something different, say a square. It would be great to be able to remove the circle vector symbol layer and add another instead, or perhaps several others to make a more complex symbol.

Example 2: polygons symbology. Similar to above, I'd like to be able to add additional vector symbol layers, in this example let's say I want to add a stippled pattern on top of the hatch fill that's already there.

Example 3: polylines, add a halo layer. In this example, let's say i'd like to add a white, thicker line behind the existing 2 strokes to serve as a cartographic mask or to highlight a certain layer or symbol class.
