For the multi part figs , it’s not hard :
There’s a “join stickfigure to…” button that let you join Stckfigure A’s “anchore node” to one of Stickfigure B’s none-static node
here are some pics for more detailes :

To join two figures , first select the one you want to join (here , the arm)

Then , press “Join stickfigure to…” and select where you want to out it (here , we’ll put it on the shoulder’s non-static node)

And BAM , both are joined. If you want to unjoin them , you just need to select the joined fig , and you have a button right next to the join button.

Keep in mind that we can’t invert the figs (join the body to the arm instead of the arm to the body) or join a none-static node with another , you can only join an anchore node to a none-static node or an anchore node to another anchore node.

If you have questions or if I wasn’t clear , don’t hesitate