@Pachuqismo,
It's quite possible I haven't correctly understood what you want but if all you need is a list of all the tags currently in use in a calibre library then that can be done quite easily with any SQLite utility. I used SQliteSpy.
- Take a copy of the file metadata.db from your calibre library and put it somewhere else.
- Open the copy with the SQLite utility.
- Open the table named tags. It has 2 columns (id, name).
- (In Windows) Ctrl-A to select the whole table contents. Ctrl-C to copy. Ctrl-V to paste it somewhere else (e.g. a spreadsheet or a .txt file)