CENTER LINE SETTING
👉 No rigging yet:
1️⃣ auto setting THEN manual

👉Rigged:
1️⃣ revert deformer to original form
2️⃣ auto setting THEN manual
3️⃣ Ctrl+Z

The previous video's temp param method can be used if you don't want to manually set the center line, since Motion Mirroring detects the center of the deformer automatically ^^

or if you want to "store" the old rigging if you want a checkpoint to come back to!