[Tarana]

I originally set up my library when I had 500+ books (now over 3,000). I downloaded the metadata and deleted all the tags. Why? Because tags for retail sale are different than your tags preferences. The way I did that was to select everything, then Right click to EDIT METADATA and do a BULK EDIT. Then click the box that removes all tags. Click apply and Calibre removes all the tags.

Ok, maybe that's too much for you. You can edit the tag or delete them under more control. Open Calibre and select TAGS. Then Right click and select MANAGE TAGS. Delete or rename tags that are already present. You can do the same thing scrolling along the side of Calibre in the TAGS table, although most of the stuff is likely in folders.

Use the tags you like and can use to find things. If I was the only user, I would just use 10 categories (general genre). However, I'm the 'keeper of the library' so have to add additional tags that would suit my family members, which is a bit more time consuming.