DesignModeler troubles
 

Whereas formerly I have imported geometry I would now like to work with DesignModeler in order to experiment with 'parameters' within ANSYS control for optimisation.
Have done the tutorials but still can't figure out:
* why should 'slice' only work on 'frozen' stuff?
* why when two bodies are brought into contact must they merge to become one, which I don't want? This occurs when extruding to next, or when extruding a sketch on one body's surface plane a fixed distance away from it, or when moving one body adjacent to another.
* why can't a sliced off separate body be selected to 'unfreeze'?
Any advice or source material for further explanations would be great.
Thanks.

Reading the ANSYS FAQ I found answer to 'slice' question and was able to extend this to my issue of bodies joining when I didn't want them too - answer is to freeze the existing body first, then they remain separate. I now realise the tree has a top down structure - undesirable outcomes can often be avoided by modification of the tree's top.
Now have to work on understanding the 'imprint' methods to deal with body interfaces appropriately.
Hope this conclusion facilitates progress of others.