I am working on exporting my maps through the layout editor, but in the generated legend the symbols are not appearing as they should. As you can see from the screenshot, the "Legend Items" displays everything I want it to display, but on the map itself, the circles are missing.
You can set the symbolization for the legend of the layout in QGIS main window. Either Go to
Layer styling panel or
Layer properties / Tab Symbology. In both cases, on the bottom, click
Advanced and select
Data-defined size legend…. Than you can choose e.g.
Collapsed legend as shown in the screenshot below.
For details see the documentation.
See the result in the layout editor: