There are no length rules or length tuning tools in CircuitStudio. The PCB panel shows the Routed and Un-Routed length of each Net so these values can be compared with other nets, for example, the two nets in a Differential Pair.
Compare the values. You will need to manually calculate the difference in length to see if it is within tolerance. If the two nets are highlighted in the panel and you press Ctrl+C, you can paste the values into a spreadsheet.
In the PCB panel there is also the Differential Pairs Editor which shows the Average Length of the pair and the Routed Length of the two tracks but it doesn't show Un-Routed length
