Just a couple of tips adding to the suggestion by silver-sun (which is the safest for important playlists, since an external file will survive an eventual database corruption):
Use Undo to fix a mistake during the current Strawberry session. Keep in mind that the undo history will be lost if you close the player.
We have starred (favorite) playlists, which are kept in the sidebar tab "Playlists" after being closed in the playlists pane (so, there's less chance of spoiling them), and are updated on the fly when open, like regular ones. To add a favorite, right click on the playlist tab and choose "Star playlist"
You may find the combination of external, regular and favorite playlists that suits you best. For example, an external as backup to save every now and then plus a favorite (even also a regular one). Or two favorites: a do-not-touch version for reference/backup and another one to play with safely.