We are currently focusing our attention on the Highlights feature. Our team has carefully reviewed all the feedback and reported bugs concerning this feature. We are in the process of evaluating which issues can be feasibly addressed in the short term.
As outlined in the Highlight documentation, which we acknowledge could be more explicit, mobile devices currently only support the Fill component of the Highlight effect, excluding the Outline. This is a result of limitations imposed by mobile GPU performance. Our team is actively researching and working on a new implementation that aims to include Outline support on mobile devices.