System Configuration : Preferences : Mixing Preferences : Automation Section

Automation Section
Smooth and Thin Data After Pass
When selected, Pro Tools automatically smooths and then applies the specified amount of thinning to the automation data created in an automation pass.
Degree of Thinning
Specifies the amount of thinning performed on automation data when you using the Thin Automation command, or if you have selected the Smooth and Thin Data After Pass option.
Plug-In Controls Default to Auto-Enabled
When selected, all applicable controls of newly added plug-ins are enabled for automation. When not selected, the controls of newly added plug-ins must be manually enabled for automation.
Suppress Automation “Write To” Warnings (Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
When selected, Pro Tools suppresses the warnings that appear after invoking any of the Write Automation To Start, Selection, End, or Punch commands and then stopping the transport.
Latching Behavior for Switch Controls in “Touch”
This option determines the behavior of switch-type controls (such as mute or plug-in bypass) when writing automation in Touch mode.
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When selected, controls in Touch mode will latch in their current state. If an existing breakpoint is encountered, writing of automation stops. If the transport is stopped while writing, the control will AutoMatch to the underlying value.
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Allow Latch Prime in Stop (Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
When selected and any tracks are in Latch mode, any automation-enabled controls on those tracks can be set to new values while the transport is stopped by touching or moving controls, to prepare for the next automation pass.
Coalesce when Removing Slaves from VCA Group (Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
This option determines the behavior when removing slave tracks from a VCA-controlled group.
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When selected, any automation on the VCA Master is automatically coalesced (without confirmation) to its slave tracks when the tracks are removed from the group.
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When not selected, a confirmation dialog lets you choose whether or not to coalesce the VCA Master automation to the slave tracks.
Standard VCA Logic for Group Attributes (Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
This option determines which Mix group attributes may be selected in the Group dialog when the group is assigned to a VCA Master.
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When selected, the Main Volume, Mute, Solo, Record Enable, and Input Monitoring controls on slave tracks follow the VCA Master only and are not available to be independently linked. (This emulates the behavior of analog console VCA masters.)
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When deselected, the Main Volume, Mute, Solo, Record Enable, and Input Monitoring controls follow the VCA Master, but also remain available for independent linking with groups.
Include Sends in Trim Mode (Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
This option determines the Trim status of Send faders when a track is put in Trim mode.
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When selected, Send faders go into Trim mode along with the Main Volume fader.
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When deselected, the Main Volume fader goes into Trim mode, but the Send fader stays in the corresponding standard Automation mode.
Include Control Changes in Undo Queue
This option determines whether certain mixer control changes, such as moving a fader or pan control, are entered into the Undo queue.
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When selected, mixer control changes appear in the Undo queue, and are undone if any prior operation is undone.
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When deselected, mixer control changes will not appear in the undo queue, allowing you to undo other types of operations without losing the current mixer settings.
Any set to default operations that affect mixer controls will be entered into the Undo queue.
AutoMatch Time
If you are writing automation in Touch mode, when you release a fader or control, writing of automation stops and the automation data returns to its previous value. The rate of return to the previous value is the AutoMatch Time.
AutoGlide Time (Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
Specifies how quickly Pro Tools transitions (glides) from one automation value to another, when AutoGlide mode is used.
After Write Pass, Switch To Options
These options select the Automation mode that Pro Tools tracks automatically switches to after an automation pass in Write (or Write Trim) mode. Select one of the following options:
Touch
Switches to Touch mode after an automation pass in Write (or Write Trim) mode.
Latch
Switches to Latch mode after an automation pass in Write (or Write Trim) mode.
No Change
Stays in Write mode after an automation pass in Write (or Write Trim) mode.
After an automation pass in Write Trim mode, tracks automatically switch to the Trim version of the specified setting.
Coalesce Trim Automation Options
(Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
These options determine when Trim automation is committed to the main automation playlist on a track.
After Every Pass
Sets Trim automation to coalesce when the transport is stopped at the end of each Trim automation pass. No Composite Playlist is indicated.
On Exiting Trim Mode
Sets Trim Automation to coalesce on a track when the track is taken out of Trim mode. A Composite Playlist can be viewed before committing Trim moves.
Manually
Trim Automation can be coalesced only with the Coalesce Trim Automation command. A Composite Playlist can be viewed before committing Trim moves.