I always had a habit flog forgetting dressage tests! Now I run around the back of my float pretending the tailgate is the judge and walk where's I need a to walk and run where I needs to trot or canter, it may seem a bit crazy but it works for me. Also in paper helps too and just before you go in say it out loud and draw it on your horses neck. Also watch the person before you!
Draw it on paper 1 million times this helps me a lot. For your jumping corse bring a white board and draw it. Put the white board on your trailer and memorize it while tacking up. You can do this with dressage if you want too
Imagine the test in your head and make the movements when walking. it might sound weird but it helps, make a little rectangular box in your brain and walk through it. Also watching other people ride your test before you really helps.
i find walking on foot in your dressage arena helps to learn your test and also walking it on your horse. Just slows it down a bit.
I'm pretty sure there is an app for learning Dressage tests :)) hope this helps !
Visualise! It helps you remember the dressage tests and will improve your performance on the arena. If your head is already used to "the moment" it'll make it easier for you when riding the tests.
I try not to ride it too many times as I then find that my horse anticipates the movement. I'd just draw up an arena or just run around the lounge room and practise it on foot!