validation on a combination of values (on submit)

[StefanHoutzager]

Would be nice to have. I think I could do in the meantime with a hidden field (not the 'hidden' component), so one (textfield f.e.) with show = false on property folder conditional section advanced. I'm using a self-written backend btw, I can call js from there to execute the validation. Btw javascript isn't enough for these validations. Best would be to use a dsl for all custom validations (that could be compiled to js and the serverside language): https://www.cas.mcmaster.ca/~carette/publications/FedorenkoThesis.pdf