The process of making custom avatar poses is relatively straightforward; with the avatar file open in BLender, a pose is created which is then exported to FBX. On import to IMVU an appropriate 'action' is created that triggers the pose automatically or manually by typing a special word or phrase.
To create a stand-alone pose, one that's not associated with any other items, with the avatar file open ensure "Pose Mode" is active, left-click in the "Action Editor" timeline at frame one to set, then right-click the bones associated with the pose being created, for example moving the arm bones to make a 'nomnom' pose that makes the avatar look like they are stuffing a doughnut into their mouth, and using the "Rotate" manipulator, left-click drag the coloured axis indicators to spin and twist the selection around its local origin. Repeat along the bone chain, taking care to avoid the mesh collapsing in on itself due to over-manipulating a given bone.
Once a bone or set of bones have been manipulated into position, from the "Pose" menu select "Animation", "Insert Keyframe", then "LocRot" from the "Insert Keyframe Menu" list ("Pose » Animation » Insert Keyframe » LocRot"). A set of keyframe markers will appear in the "Action Editor" timeline. For 'static' poses that make the avatar appear frozen, once this initial frame is marked, left-click the timeline to set another frame, at frame ten for example, and again "Insert" the pose; "Pose", "Animation", "Insert Keyframe", "LocRot". This duplicates the pose across several frames.
Left-click again a few frames along the timeline, at frame twenty for example, and from the "Pose" menu select "Clear Transform", "All" ("Clear Transform » All"). Insert a final keyframe of this reset pose; "Pose", "Animation", "Insert Keyframe", "LocRot". to finish the action. Left-click dragging the timeline slider back-and-forth now will show the avatar pose transform from one pose to another, this change is important for FBX export.
To export, toggle into "Object Mode" from "Pose Mode" ("Ctrl+TAB") then select "File", "Export", "FBX" ("File » Export » FBX (.fbx)"). In the File Browser that appears change the file name and save location as required, in "Armatures" deselect "Add Leaf Bones" then click "Export FBX" top-right. Blender will save an FBX file ready for import into IMVU.
To import the pose, in IMVU derive from the appropriate product and once loaded click the "fbx import" tab, then on the "load fbx" button top-left of the section. A File Browser will appear. Browser to and select the saved FBX file and click "Open". In the "Select Skeleton Root" pop-up that appears select the skeleton associated with the pose and click "Configure FBX" to load the data into the importer.
Here a number of subsections will list the files components under "Skeleton", "Meshes", "Animations" and "Morphs" depending on what was included at export from Blender, for poses an entry under "Animations/Actions" will be shown. Make sure this is selected then click the "Import" button to convert the file, then finally click "Apply Changes" making it ready for assignment to an "action" as normal.
Depending in the product derivation, to add the now available pose, create a new "action" in the "actions" tab by clicking the "Add" button, give the action a "Trigger", for example "nomnom"; set the "Type" to "Avatar"; enter a value in "#ensembles played" that reflects whether the pose plays a fixed number of times or infinitely, and change "After Playing" to "Pick same ensemble". Then in the "Skeletal Animation" section below, select the imported pose file from the XAF drop-down list; change "Composition" to "Replace" and set a "Loop start" and "end" point that matches the pose frames previously marked in Blender, for example frames "2" and "9". Then set "#loops" to "0" to loop infinitely.
Click "Apply Changes", test, then save and publish.