Hey there @msilva !
can I update a TEA value from a Program Stage?
If you mean whether you can open a program stage, change a value in that stage, and have this directly affect the TEA values - this is not possible. No assign rules will affect data outside of its own context - or seen from the user prespective, outside of the form you are working in.
If you make such a rule that assigns to a TEA value, the user would have to upen the profile widget before the assign rule is triggered.
It does seem like it would be useful to allow updating TEA even without opening the profile form - but this needs proper treatment as a feature request. We would for example have to have a way of handing if the rule wanted to update a TEA value to an illegal value. We would also have to make sure the user sees that an update is made out of their own context.
We do have a roadmap idea that also seems to play into this, and would possibly be of help: Log in with Atlassian account
This item describes functionality to re-run program rules outside the data entry context itself, and it does seem like an opportunity to discuss updating the TEA values as well - these rule re-runs could assign the value you wanted based on data in a program stage.
The screenshot above and in the documentation seems like a plain error in the docs that we should fix. The example shows a Tracker program, and therefore the TEAttrubutes should be possible to select in the assign dialog. It was not removed on purpose, and on @Karoline inspection, it seems the error has been there quite a while.