If you want to store a sample you can easily find a free location by clicking on the Search free location button in the inventory browser. Highlight the storage location in the navigation tree by selecting the storage unit in which you want to store a sample and click on the Search Free Location button
You may use the heatmap to get a birds-eye-view of a complete storagunit and its space utilization. Green colors represent empty spaces, yellow filled spaces. Red colors represent (near) full spaces.