Use fields as well as Master Items in "My Sheets" area in a published app whether from On Prem or Saas.
When you publish an app from Qlik Sense SaaS to a Managed Space, the Fields and Master Item can be used when editing in the “My Sheets” area
When you publish an app from Qlik Sense Client Managed to a SaaS Managed Space, only the Master Items are available when editing in the “My Sheets” area.
The argument that you should always use Master Dimensions falls flat since the fields are offered when amending charts on published apps in "My Sheets"
Support have advised that I should set this up as an idea as they say it is how it is meant to work because this is the way it now works in Client Managed, the fact that it is not the way it works in SaaS seems to be irrelevant.
It should allow fields to be applied as ad-hoc changes normally apply to fields that have not been set up as 'Master Items' and for ease of use.