Project WBS consist of different number of task, each of them linked to different number of categories (sub-task in Estimated cost and revenue tab).

According to field order in Expense journal line users suppose to register actual expense in this order: 1. Select ProjectID, 2. select Activity number, 3. select Category.

There's no relation between lookups in fields Activity number and Category - the two lists shows all elements (if no Project/category validation list exists). My suggestion is Category lookup to be limited only those categories, included in WBS under selected activity (task).

Different customers have different requirements on WBS - some of them have large number of activities but only few categories linked to each task, the other have few activities linked to large number of categories. 

It'll be great if there is parameter to state preference order of fulfilment of fields Activity number / Category. If users prefers first select Category then the field order in journals  should be changed (1.ProjectID, 2.Category, 3.Activity number,) and the lookup of last field, Activity number, should show only activities (task) to which  selected Category is linked.

Please also show Activity number in WBS to be easy to trace information in posted transactions and compare to WBS.