I understnad it might be a lot of work to split complex workflow to several smaller ones.
but if you are already at the edge to be able or not to publish wiorkflow, there is not an other way.
you could save some room for modifications if you delete some actions that are not realy needed for business logic itself (logging, notifications, action sets, disabled actions,....) but soon or later you will anyway come to the point when you'll have to split it.
As I'm using Demand Management Workflow, I can't use sub workflow
I'm not sure what you exactly mean with "Demand Management Workflow", but I guess that's just your workflow name. that shouldn't restrict you to create/start subworkflows
Apparently Subworkflow only works with Site Workflow
to be able to configure Start workflow action to start any other workflow, the workflow has to existing on the (same) site. regardless of whether they are list or siet ones.
it is complicated to split my worlfllow in smaller subworkflows because a lot of data from one branch are used in others ones
there shouldn't be a problem to hand over data between workflows back and forth.
to pass a data into a child workflow being started, create within the child workflows respective variables and mark them 'Available on start form'. they then appear in start workflow action as a separate entries and you will be able to configure what data should be passed in.
to retrieve data from child workflow use store/retrieve data workflow actions
