As far as I know, parameters are “set once, read only” data. If you want runtime parameters, you have to
- Make a task, global task or evaluator where the variable will be calculated.
- Make your variable in this object.
- Make it instance editable (click on the eye), or in C++ make it VisibleAnywhere or EditAnywhere (I believe either should work)
- Move it to the Output category. It must be spelled correctly, it won’t work otherwise.
- Add the task or evaluator object to the tree. If you did everything correctly, you should see a gray bubble saying OUT and you won’t be able to bind to this variable (since you’ll be writing to it)
- Set this variable only from this object.
Other tasks and evaluators can then bind themselves to read from this variable.
This is a poorly documented feature, but I got it to work doing these steps.