In most word processors it is possible to assign keyboard shortcuts to the various functions of the Zotero word processor plugin toolbar (i.e. add citation, edit citation etc.). How to do this depends on your word processor.

1. Open Tools→Customize…
2. Click on the key to you want to use, from the list of assignable keys in the top portion of the dialog.
3. Find the appropriate Zotero macro in the bottom part of the dialog. The macros are in LibreOffice Macros → user → Zotero → Zotero. Click on the desired action in the list (probably ZoteroAddCitation)
4. Click the “Modify” button.
5. Click “OK” and enjoy!