Can styles in ArcGIS Pro be exported to apply to another map?

Answer

In ArcGIS Pro, symbols or style items have to be added to style files individually. This can be done by adding new styles or by clicking a symbol in the Contents pane or the Symbology pane to open the Format Symbol pane, and from the menu button at the top right, click Save Symbol to Style. More information on this can be found in the document: Save symbols and style items in styles

Equivalent ArcMap functionality does not exist in ArcGIS Pro, but there is an open enhancement. There is also a workaround in the Esri Community for exporting the styles from ArcMap to bring into ArcGIS Pro: ArcGIS Pro "Export Map Styles" for bulk saving of symbols

Follow the instructions below to copy styles from ArcMap and bring them into ArcGIS Pro:

1. In ArcMap Go to Customize > Customize Mode > Commands, search for the tool Export Map Styles, and add it to the active toolbar. Save the style as a .style format. 
2. Open ArcGIS Pro and add this .style file into the Styles folder. Create a new .stylx in ArcGIS Pro. 
3. Right-click ArcMap's .style, click Manage, and press Ctrl + A to select all symbols, right-click, and click Copy. 
4. Right-click ArcGIS Pro's .stylx, and click Manage. Right-click and click Paste. This brings all the symbology into ArcGIS Pro's .stylx format. 

The symbology can also be saved as a layer file and the styles imported to other layers. The following documentations provide some information on that option:

• ArcGIS Pro: Save a layer file
• ArcGIS Pro: Apply Symbology From Layer (Data Management)