Use Case is along the lines of:

• I have an existing timer event for which the duedate is calculated using an expression
• Something changes in the context of the process (internally or externally) which should lead to a re-calculation of the duedate.

Currently this is not easily possible. I can either

• calculate the new duedate externally and then update the timer via the management service. Disadvantage: the condition is not re-evaluated, instead I need to re-calculate the condition externally
• use process instance modification to cancel the timer and re-enter it. This leads to a re-evaluation of the expression but it has many drawbacks like messing up history, concurrency inside the process instance etc ...

Goal of this issue is to come up with a solution allowing to address the use case in a better way.