This document talks about how to use window "Database manager". Database manger window can be open from menu Tools => Database manager.
LetmKara save song-list in JSON format in file listsong.json in folder db. So this is not quite a database, but just a table in database. Normally you don't need to touch this file, but if things go wrong, you will know where to look and what to delete to reset.
To add, click Add and select folder that contains songs.
To remove select a folder and click remove
Click Scan all to scan all folders and add songs to database.
Options in this window
There are 3 checkboxes:
Clean database: delete all data before scan, meaning a whole new database.
Delete cache files. LetmKara saves a file cache.json in each folder where it scan for media files. This file is a fraction of database, which contains data of that folder only.
Show more options for selected folder: if you select one folder in the list (added by button "add"), this checkbox will be enabled for you to check. After check, you can change text encoding for that folder. Nowaday, Unicode is common, but before old karaoke songs are encoded in various text-encoding. This setting will make sure karaoke text is displayed correctly. There are also button "scan" and checkbox "delete cache" for the selected folder only.
This tab is meant to manipulate database and test only. Use at your own risk.
Clean up missing is to remove songs that don't exist on disk but still in database.
Re-generate data is to regenerate data to help searching.
Use test search, you can manually change data in database.