Update
2019/8/30    Append how to add flavor animations.


Introduction
There are many pose mod such as Dave's Poses and Pose anyway.  They contains idle animation files and we can call them via console
command e.g. player.playidle *****.  But It should be useful if we can
make interactable Workshop objects (like chairs) which automatically
call desired idle animations.  In this tutorial, I explain how to
realize it.  For demonstration, I'll create a new chair using an idle
animation motor3 in Just a pose mod.  The corresponding animation file is Meshes\Actors\Character\Animations\My Poses\motor3.hkx.

1. Prepare Animation files
Three HKX files are needed: EnterFromStand.hkx, PoseA_Idle1.hkx, and ExitToStand.hkx.  PoseA_Idle1.hkx is the main animation file.  You only have to rename motor3.hkx to PoseA_Idle1.hkx.  The others are used on entering and exiting literally.  Let's reuse vanilla assets for them.  I often use
     - Meshes\Actors\Character\Animations\Quest\RailroadHQ\Looking_TacticalMap_Stand\EnterFromStand.hkx
     - Meshes\Actors\Character\Animations\Quest\RailroadHQ\Looking_TacticalMap_Stand\ExitToStand.hkx
because they are versatile. The HKX files should be located in one directory.  In this tutorial, let's put them in Meshes\Actors\Character\Animations\Furniture\MyChair01



2. Create Plugin
Open Fallout4.esm with Creation Kit. 

[Keyword]
Create a new Keyword e.g. AnimFurnMyChair01.
    

[Race]
Duplicate HumanRaceSubGraphData and rename it e.g. HumanRaceSubGraphDataAdditiveTutorial.


Open HumanRaceSubGraphDataAdditiveTutorial - SubGraph Data. Select Additive and HumanRaceSubGraphData as below.


Click "OK".  Reopen.  Create a new subgraph entry as below.



[Furniture]
Let's reuse a vanilla chair record NpcChairPlayerHouseRuinKitchenSit01.  Open and edit it as below.
    

Click "OK" and "yes".  Reopen.  Then, let's make it assignable object.  Attach workshopobjectscript.
    

Set the script property WorkshopParent as below.


Add Keyword WorkshopWorkObject and set Actor Value WorkshopResourceObject to 1 as below.


[Constructible Object]
Let's reuse a vanilla record workshop_co_PlayerHouse_Ruin_ChairKitchen01.  Open and edit it as below.


[Save]
Save as e.g. FurnitureTutorial.esp.  Let's check it by FO4Edit.  You should see four records.



3. Create Metadata
If your ESP file name contains spaces, remove it tempolarily (e.g. Furniture Tutorial.esp --> FurnitureTutorial.esp).
Move to Fallout 4 directory (e.g. ***\Steam\steamapps\common\Fallout 4).  Right click Data directory with Shift key down.  Open PowerShell (Windows 10) or Command Prompt (others).


Run below command.
..\CreationKit.exe  -GenerateAnimInfo:FurnitureTutorial.esp  .  Data\

(Don't care "Yen" character takes places of backslash. It's due to my locale)

Creation Kit starts and terminates automatically without any messages.  But you can see it output some text files in Meshes\AnimTextData. 
Now you can revert your ESP file name (e.g. FurnitureTutorial.esp --> Furniture Tutorial.esp).


4. Check in Game
Don't forget to activate your plugin.  You should find the new chair in FURNITURE > CHAIRS.


When you use it, you will find bad positioning.



5. Position adjustment
Open MyChair01 with Creation Kit.  Change Marker Position/Orientation.


That works!




[Optional] Add flavor animations

6. Prepare Animation files
Drag & drop & rename.



7. Find hash number of the animation
Move to Data\Meshes\AnimTextData\AnimationFileData.  Activate File contents search.


Search for "MyChair01".  You will found the relevant text file.  Copy the number 3091264521319256988.



8. Create dynamic idle metadata
Move to Data\Meshes\AnimTextData\DynamicIdleData.  Create 3091264521319256988.txt as follows:
Version 1
Actors\Character\Animations\Furniture\MyChair01\PoseA_IdleFlavor1
Actors\Character\Animations\Furniture\MyChair01\PoseA_IdleFlavor2
Actors\Character\Animations\Furniture\MyChair01\PoseA_IdleFlavor3
Save with LF newline.