There is an issue when using the task planner (I tested this with Request Tasks) that if there are certain fields (specifically the category and the model) are not on the request form or they are invisible that in the task planner you cannot select an "end phase" since the corresponding drop down list is not populated.
This can easily be reproduced by:
- cloning the OOTB form for a request, e.g. rm.request.logging
- dropping the category and the modelname or making them invisible
- trying to define a task in the task planner and trying to set an "end phase"
From my perspective this is a bug that should be fixed because it is not obvious why the SM task planner depends on these fields (or their visibility condition). The information should be rather fetched from the record than from the form. But even then, the information about which workflow phases exist and which transitions exist is there because that's exactly what's being displayed on the workflow tab.
If this dependency to the fields o the form is not removed through a code change then at least there should be documentation about which fields can be safely removed from a form without breaking tool functionality. There may be other cases where some internal function depends on fields on the current form beyond my particular example.