Animation Blueprint Library
Right-click in the graph of the Anim Modifier Blueprint to see the context menu and list of functions available, particularly under the Animation Blueprint Library.
In the image above, functions related to Marker Syncing are expanded which enable you to synchronize animations using marker data.
Before working with the various functions available for accessing data, you will want to implement the OnApply and OnRevert events.
The OnApply Event enables the user to change, add or remove data from the animation while the OnRevert enables the user to remove previously applied user changes (or return the sequence to its original state).
Each event returns the Animation Sequence in which to feed the Animation Blueprint Library operations.
In the image above, when the Anim Modifier is applied, a new Notify track is created with the defined name while reverting the Anim Modifier, the track is removed.