Enhanced ankle mobility during testing and corrective exercises is only as useful as its ability to transfer into function. This is one of the reasons why many mobility programs don't achieve notable results for long, and are extremely short lived.
In order to extend the life of your ankle mobility and habituate it for the longevity of your training career, you must train into the new range of motion and facilitate motor learning. One of the most effective ways to battle-test a new range of motion is by strategically loading it in a way that's intended to elicit a training effect.
If ankle mobility continues to be your one major point of dysfunction, there's no better time to train the lower legs directly than first exercise in a lower body training day.
Chase a pump in the calves before stepping into the squat rack. Focus on stretching the calves in the bottom position for a full second on each rep, driving up, and flexing the calves during peak contraction. Then, lower slowly into the stretched position. Execution is pivotal if you want this to increase your mobility.
One of my favorite ways to prime the ankles and get a quick and nasty pump is with an escalating pyramid scheme that climbs in weight while using 8-12 reps per set. Keep the rest periods minimal – anywhere from 15-30 seconds – to accumulate blood flow into the targeted tissues and create one hell of a mind-muscle connection.
Warning: Squatting for the first time with a huge calf pump will feel strange, but keep it in your workouts for 3-4 weeks. Then watch your mobility improve and your numbers sky rocket.