Github user sergeymazin commented on the issue:
https://github.com/apache/zeppelin/pull/2120
Issue we are facing is when somebody else is adding/renaming/deleting any
other notebook, unsaved text in current notebook is lost.
Renaming any other notebook resets current notebook:

Deleting any other notebook resets current notebook:

Same comes with adding/importing new notebooks. This makes Zeppelin
unusable when working in multitenant mode once somebody starts
importing/renaming notebooks.
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