Tomas Slancik

you can't

addpoint(), setpointattrib() and many other functions that allow creating/writing data to new or non-current element are queued to be executed later as a single threaded operation

furthermore point() or other functions that query data currently query the input geometry even if geoself() is used, as currently geoself() just returns 0 which is the cached first input geo

so currently writing/reading the newly written values within a single wrangle is limited to current element only using @ binding

EDIT: or if you are running within Detail wrangle you can probably store the values in an array to keep track of them yourself

glad to help, once you are happy with manually created graph as a prototype, next step would be creating it as a more procedural APEX script component so that it supports variable number of joints and blendshapes

while I have some rigging and programming background, I'm not up to date with specific APEX and Python houdini tutorials, but I'd just search the Learning Portal for APEX, there is already quite a few covering various parts of APEX, including APEX Script

if you want to link arbitrary animation to the abstract slider, I'd recommend using motionclips instead of blending individual poses
that way motionclip can provide complex animation consisting of large amount of poses and you just evaluate it in APEX with your abstract control mapped to the motion clip range

example attached

here is a take on fixing the scene and the graph manually
I also added the FK controls on top of blendshaped skeleton where animator can apply further offsets

for reference some of the things that were updated:
- skeleton blendshapes are no longer packed as their points need to be accessible by APEX
- changed the Rigpose nodes to just apply rotations to joints, since offsetting the joints creates wrong deformation due to resulting orient misalignment of parent joints

in graph:
- added dict entry for base skeleton and fixed weight key from blend# to weight#
- fixed weight values to increase and decrease for specific regions
- added ability to have manual FK controls on top of blendshaped pose