Open Custom fields, click Find fields to list the meta keys found on your records (WooCommerce's own internal keys are hidden), or add a key by name. For each key choose a column name and a cell type: Text, Rich text, Number, Checkbox, Date, Select, Multi-select (options as value:Label, one per line), Image, Gallery, a list stored by a plugin (advanced) or JSON (advanced). Switch it on and Save and reload. The column then loads and saves like any other. Keys are used exactly as stored, capitals and spaces included (WooCommerce's PayPal handler, for one, writes a key called Payment type). Gallery and multi-select fields are written back in the shape they were found in — a list stays a list, a comma-separated value stays comma-separated.

Text, Date and Select values are saved as typed, trimmed at either end: percent signs and codes such as Yoast's %%title%% %%sep%% %%category%%, Rank Math's %category% or a link's caf%C3%A9, a lone < as in "sizes <38", several spaces in a row, line breaks and backslashes are all kept. A Select or Multi-select option's value is kept as typed when you define it, so 30%BF:Black Friday offers the value 30%BF; its label is shown as text and never holds HTML. Lists, multi-selects and JSON values keep their text the same way, backslashes included, and a JSON value with a quote or an accented letter in it is still what you typed when saved. A value with HTML in it is kept as written for anyone allowed to post unfiltered HTML (administrators on a single site, super admins on a network) and cleaned for everybody else, as a product description is; that goes for the keys of a list or a JSON value too. Earlier versions took every % followed by two of the characters 0 to 9 and A to F, capital or small, out of these values and out of Select options, folded spaces and line breaks into one space and wrote a lone < as <. On products, coupons and reviews they also took the backslashes out, which left a JSON value with a quote in it unreadable and saved an accented letter such as é as u00e9; on orders a list lost them the first time it was saved. A value saved like that stays as it is until you type it again, and damaged Select options stay until you correct them in Custom fields and save.

On the Products editor, Taxonomies lists other taxonomies registered for products (from other plugins); switch one on to edit its terms as a column.