1. How to export Specification Tree in CATIA?

When you want to export your specification tree, go to Save As and select text file. You will get a text file that contains only your specification tree.

2. How to lose the external references in CATIA?

It is not possible to work with external references for kinematics joints in DMU Kinematics V5. DMU Kinematics reduces automatically the number of degrees for the kinematics. The user suspects that he or she misunderstands at first, when the popup menu appears saying "kinematics overconstraint," etc. Switch off the option keep external references.

3. How to collapse the tree in CATIA?

The very useful way to collapse the tree in one go is by clicking on a single icon.

The Method:

Tools/Customize/Commands
Select All Commands from the Categories list (at bottom).
Select Collapse All from the Commands list Select Show Properties.
Select an icon button Select Tree icon at the bottom right corner of Page 1 (or any preferred icon).
Select Close.
Select Collapse All (text) in Commands list and drag onto the update icon on the bottom toolbar (or any preferred icon).

Once this is selected in that workbench, your specification tree will collapse. You need to do this for all the workbenches you use it for; i.e., Part Design, Assembly etc.