No, it is not possible to merge two web maps in ArcGIS Online. However, as a workaround, the hosted feature layers from one map can be added to the other to create a single web map. To do so, follow the steps below:
- In ArcGIS Online, open the first web map, copy and save the feature layers. For more detailed steps, refer to ArcGIS Online: Copy and save layers.
- Open the second web map and click the Add > Search for Layers option.
Alternatively, copy the URL of the hosted feature layers and add the layers to the second web map.
- From My Content, search and add the layers saved from the first web map. For more information, refer to ArcGIS Online: Search for layers.