It's pretty standard to customise the search rail for assets but has anyone ever customised the search rail for workflow inbox? Let's say I wanted to add a different facet to filter the inbox items. I don't see any documentation regarding this anywhere and naturally would be very interested to know if anyone has done this. I have attached a screenshot and marked up the section that I am alluding to.
Per the OOB implementation, InboxItemFilter(com.adobe.granite.workflow.exec.filter.InboxItemFilter) implementation specifically looks for/handle these standard set of OOB highlighted facets/predicates in InboxOmniSearchHandler(com.adobe.cq.inbox.impl.omnisearch.InboxOmniSearchHandler)
Customization will involve custom OmniSearchHandler(com.adobe.granite.omnisearch.spi.core.OmniSearchHandler) and custom InboxItemFilter implementation. (rewriting whole of the implementation and its huge change)