Which of the following can be used across all the visualisations in a workspace?

The user experience filter is the correct choice because it allows users to apply a common filtering mechanism across all visualizations within a workspace. This helps maintain consistency in the data views for users interacting with the analytics, ensuring that any applied filter affects every visualization in a cohesive manner. Consequently, it enhances the analytical process by allowing for a streamlined approach to exploring data trends and patterns.

The other options serve different functions that do not span the entirety of a workspace in the same way. For instance, signals are alerts tied to specific events or data thresholds, dashboard builders are tools for creating dashboards but may not directly apply filters across visualizations, and the studio typically refers to a development environment for building applications rather than a feature for managing visualizations across a workspace. These tools and functions are useful in their own contexts, but they do not provide the overarching filtering capability that enhances the user experience across all visualizations.