Hi Nikolaos,
I am seeing the same thing. If I add anything in the alias, I am not able to save the join. Also, I am not able to delete any of the prefilled table entries unless I first click to add one.
Just noticed something regarding the alias’. If I add an alias I cannot click ok. But, if I add the alias, click ok and the delete it and click ok again, the dialogue box closes and the alias is appended to the query.