Currently, you can only pin Signals to Elements in Explorer. This will change: The functionality will be making it to Insights!
We will be bringing the functionality to pin Signals to the Insights module. It will be available when an Insights Preset is selected, or if you are in an Element context. This allows you to quickly capture interesting information and weak signals when scouting new topics without having to create an Element.
Disclaimer: As with all upcoming product features, this is still subject to change. The entire feature or parts of it might not make it into the final product.