We would like to have conditional input fields. Like descripbed in this post: Validation in content types
Example:
A subcategory only visible/accessible if a spesific category is chosen.
Is this possible?
You could use OptionSets: several options (either single- or multi-select), each of which can have an underlying form of inputs. So, if an option (a specific category from your question) is selected then an underlying subcategory will be shown underneath and can be selected.
As Alan says, please try out optionSets, which is what we have available now. We have discussed a more advanced approach to solving this, than just conditions. There will typically be increasingly more complex scenarios desired to solve, i.e. if value a is selected i field 1, limit seleciton in field to etc.