A project can carry four disciplines, and there is no way to add a fifth. Once you have four, every other card in the picker fades and stops responding, and selecting one anyway returns "Maximum 4 disciplines allowed" instead of adding it. The limit is the same for every project and every plan, so upgrading does not raise it.
The picker sits in the project editor, under Select Disciplines.
To swap one, take one off first
Disciplines toggle rather than stack. Selecting a discipline you already hold removes it, and the rest of the list becomes selectable again straight away. The four you hold are unordered, and none of them counts as a primary discipline, so there is nothing to rearrange.
The list is fixed, and you cannot write your own
Disciplines come from a catalogue uni maintains. You can search it, but you cannot invent a discipline that is not on it, and neither can anyone else. That is what makes them worth filtering by: two projects carrying the same discipline really are describing the same field. If you want your own wording, that is what tags are for, and they are a separate field.
Four is a filing limit, not a description limit
Disciplines are how uni sorts your work, so the cap exists to keep that sorting meaningful. Your four decide:
- Which projects yours is shown alongside. The similar projects strip on your project page is built from them.
- Which competitions are suggested below your project.
- Whether your project is found when someone filters project browse by discipline.
- Part of the page's search keywords, which is how a search engine reads what the project is about.
They also appear on the project page under Associated Disciplines, each one linking through to that discipline. A fourth pick that only loosely fits will pull your work into a stream it does not belong in, so three accurate disciplines beat four for the sake of four.
A discipline change waits for your next publish
Changing disciplines edits your draft, exactly like editing the title or the description. The live page keeps the disciplines it was published with until you publish again. If you have changed them and the public page still shows the old set, that is the reason, and publishing fixes it.
Disciplines are not part of version history, so restoring an earlier version never changes them. What version history records covers the rest of that boundary.