How to change symbol size in QGIS map composer legend?

Just for anyone that may still be looking around for an answer to this issue, I havent managed to find a feature within QGIS either... but i have figured an effective way of compensating for the issue.

I simply add an image box into the Print Composer and use an corresponding image (Usually .SVG files) to cover the previous symbol that is too small. I understand its not the best way to get around the issue but its much quicker than creating and duplicating layers.

I hope this helps anyone with similar issues.

As far as I know there is still no solution to adjust the symbol size of point features inside the QGIS composer. The symbol entry works only for polygons and lines.

However, a workaround that was not mentioned yet is to export the map as an svg-file and open it with Inkscape for example (Inkscape is open source). There you can manually adjust the symbol size for every legend item.

Since QGIS 3.14 you can change the change symbol in the legend.

In the layout select your legend, go to item property, then double click on the legend item you want to edit.

Check the custom symbol checkbox and by double clicking on it you can configure the size or color or symbol that would be used in the legend only.

Note : If needed you can find information on how to display polygon as a line