A tongue is rarely one thing. It can be pale and purple, with a thin white coat, swollen and cracked, and a field that only lets you pick one of each makes you choose which part of what you saw to leave out.
As many as apply, in three groups
On the Pulse & Tongue tab of a session, the Tongue section has three groups: Body color, Coating and Shape. Each is a row of chips you click to turn on or off, and any number can be on at once. Each group has a filter box above its chips, so a few letters narrows the list. The chips are listed alphabetically.
The starting lists are Pale, Pink (normal), Red, Deep Red / Crimson, Purple and Bluish-Purple for body color; None / Peeled, Thin White, Thick White, Thin Yellow, Thick Yellow and Grey / Black for coating; and Normal, Swollen / Puffy, Thin, Cracked, Tooth-marked, Stiff, Trembling and Deviated for shape. They are only starting points.
A term that isn't listed
Type it into the group's filter. If nothing in the list matches exactly, the last option becomes + Add followed by what you typed. Click it, or arrow down to it and press Enter, and the term is switched on for this chart and added to your practice's list in the same step. The next chart offers it as a chip like any other. Typing a term that is already there, in any capitalization, just selects the existing one.
The three groups are their own lists, so a coating you add doesn't appear under shape. They are the same lists you curate under Settings → Charting → Clinical vocab, as Tongue body color, Tongue coating and Tongue shape, where you can rename, remove, reorder or reset them. Renaming a term asks you to confirm when charts already use it, and updates those charts. This is the same mechanism as for pattern, pulse and technique, described in your own clinical vocabulary.
Where it shows up
The This session so far panel reads the tongue as one line, with the groups separated by a dot, such as Pale, Purple · Thin White · Swollen / Puffy, Cracked. Clicking it jumps back to the Pulse & Tongue tab. The same line appears in the chart PDF and on the read-only chart.
In session history, a tongue edit appears as Tongue changed. Expanding it lists Body, Coating and Shape with the before and after for each group that changed, so you can see that Cracked was added without hunting for it. A protocol can hold a tongue too, and applying one adds its terms to the chart without duplicating any you already picked.
Practices that name the section differently, or chart no tongue at all, can do that per chart under chart templates. The Pulse & Tongue tab is part of the TCM chart.