Hi mti,
Building selectors with dynamic content is currently not supported for native app mobile selectors.
While we do plan to support this in the future, there are alternatives that can be used in the current version to make this work (assuming that what you want is to type text into the field).
Try this: In Indicate/Edit Target mode you should be able to use the fuzzy selector (with a potentially lower threshold) together with an anchor on a more static element to achieve the same result.