I've found a bug when selecting fixtures in 2.3.0 running 64bit version under windows 10.
Starting from a blank page if you select a fixture from the palette and place it on the page, if you then select a top hat or barn door then LXFree prompts "Do you want to add an accessory to the selected lights?". If you select yes then the accessory is added correctly - perfect!
However if you now try to select a different fixture from the palette then nothing happens when you click on it - adding accessories seem to break the fixture picker palette.