Sorry to hear that the workaround doesn’t work for you, @Matias_Poisson. It isn’t possible to place the custom currency property field on the same line as the amount property but you should be able to add it just before it (= in the line above). I just tested this successfully:
Here is the Deal creation form after the changes were applied:
Please note that the required fields functionality is currenctly in beta and may not be switched on in your HubSpot portal.
Also, great to hear that this hack works for you, @Simpleselling!