Currently you can only filter by set fields within set entities. These entities and fields can be found here:
This is extremely restrictive for businesses that operate without relying on these entities or the specific field within them.
Lets use SALES FUNNEL: LEADS TO OPPS as an example which only allows us to filter by: Source, Dynamics Campaign, Product, Country, Business Unit:
We do not use the 'Product' entity on our Leads. Instead we make use of the 'Account' entity. On the leads that we generate it shows which 'Account' a potential customer is interested in, NOT which product.
If we could filter by the 'Account' entity and the 'name' field within this entity then we would have far greater insight through intelligent dashboards. Currently we are only able to see our lead sources and not which Accounts our customers are interested in.