@GoddessSims After having a quick trawl through the web I found two videos that cover aspects of this:
How to Use Poses with Props by ElectricBF Sims Go to about
1:40 for the main section on moving items into place in game.
Sims 4 Tutorial Pose making (accessories etc) by Shibui Sims. This goes into far more of the construction side of things within Blender.
As ElectricBF says in her tutorial, holding down Alt whilst moving objects is also really good in game for tweaking object positions beyond the usual "hit boxes", and can allow you to really customise your creations to a much greater extent.
As far as I know there is no way as of yet to completely seamlessly intergrate objects into poses or animations using pose player. Someone would have to try and write an ingame mod that opperates in a simillar way to the interaction tunings you have for pre-existing reading and cooking animations, where "props" are called to be a part of the actions.
Hope this helps