Workflow's properties that could be used in this conditional filtering are id, name, description, categoryName and version. So currently it is not possible to use categoryId in a condition, unless we add some code to do so on vRO server side (feel free to open a PR about it).
There is a workaround, though. You can get the same result in two steps:
1) Make a GET request to fetch the category with the given categoryId. It could be something like:
The returned response content should contain a href to the category object. Look for a link element that looks similar to:
<link href="https://10.20.30.50:8281/vco/api/catalog/System/WorkflowCategory/ff80808165ed93fd0165ed955493000f/" rel="down">
2) Using the value of this href element, append workflows at its end (that's the name of the relation from the category to its child workflows). The URL should look like:
Now, if you make GET request with this URL, you'll get the list of workflows that are within this category.
Hope the above makes sense.
Excellent, that works great - thanks a lot!