If it is annoying to you, that the tree is zooming out and in after clicking on any branch, you can switch it off in CATIA options.
All you have to do is to go to Tools®Options...®General®Display, in Tree Manipulation tab you can find option Tree zoom after clicking on any branch, as shown on Fig.1
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| Fig.1 |
You will still have an access to the tree, to control its size, by clicking on the small axis system in the right bottom corner of the window (Fig.2).
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| Fig.2 |