Turn to Reference: Reference Dimensions - Independent

When a sketch is regenerated or updated due to changes in external references, changes in other sketch dimensions, changes in the sketch geometry, etc., the reference dimensions change their value accordingly. However, an "independent" reference dimension retains its original value.

In the example below, the sketch is over-defined:

L4 is turned into a reference dimension:

If L3 is deleted, L4 becomes "independent":

If L2 is modified, the independent reference dimension L4 retains its original value: