Name your ledger and edit your lists. The layout is built for this kind of business and stays fixed. Changing lists never deletes items.
This ledger is saved in this browser, on this device only. Back up regularly, and always before you clear browser data, switch browser or computer, or install a new version.
Back up now saves everything (items, history and settings) to one file ending in .json. Export CSV saves just the item list for use in a spreadsheet.
Bring in a spreadsheet saved as CSV. The first row must be column headings, and only Name is required. Items are added to this ledger and nothing is overwritten. Up to 500 rows at a time.
Your items are kept only while this tab is open. The full suite saves in your browser for good, and adds backup and restore, CSV import and export, and a Pro edition with multiple locations.