Add data from Portal

[VictorRutherford]

Please include the option to "Add data" so users can add additional layers available through their enterprise portal to the layers pre-defined in the webmap they are using. We want to keep our webmaps lean and targeted to a given purpose, but users may want to add additional information or context to the site they're viewing, so rather than having to go back to portal and add the layer to the webmap and reopen it in Field Maps, it would be great to give this option to the user themselves. Especially since we may not want to keep this and other requested layers in the webmap permanently going forward, ballooning the layer list.