Hi @mazeyrat,
I talked with one of the developers and we think that this is also the same underlying issue as the bug mentioned in your other posts: [BUG-13990] Ignition 8.0.2-2019-05-09 - designer freeze when creating an UDT instance and Ignition 8.0.2-rc1 - udt instance are very long to create
We’ll update you when its been fixed.