After a back and forth with support today, I'm stuck. I'm being told there's no fix, nor will there be any changes to the functionality of this. I created a custom basemap. Basically just the outline of an area. I also have built an experience builder app to house the webmap with all of my data. Inside the experience builder, I'm using the basemap switcher widget. When loading the EB app, my custom basemap group shows up in the basemap gallery widget EXCEPT for the single custom basemap I created. The strange thing is that the custom basemap DOES show up on the map initially. The problem is, when you switch to a different basemap, there is no way to toggle the original custom basemap back on unless you refresh the entire map. Not a huge deal until you find that there is no "return to previous map state" options for experience builder. Basically any navigation you've done is long gone on a refresh. Does anyone by chance have a work around for this?