Pro Tools provides two different methods to resume writing automation on controls that were active at the point where the transport stopped:
Lets you manually resume writing automation in Latch mode. Join is available only with supported control surfaces.
After a Latch automation pass with AutoJoin enabled, the AutoJoin indicator appears in the Pro Tools Edit window.
The AutoJoin indicator is a vertical line that signifies the point where the last automation pass was stopped, and the point where the “join” will automatically occur on all tracks that were writing during that previous pass. When automation writing is resumed from this point, the line disappears.