How can one model an unconditional decision in an activity diagram?

Question

For example, the user can perform action A, action B or action C in a tool. Whether they choose A, B or C, the order of these actions and how many times they are repeated is up to the user and the reason why they choose A,B or C and why they are chosen in a particular order isn't clear. Also any action can be repeated again after another action has been done by the user.

EDIT: A more concrete example would be the creation of an image. The user can draw a shape, choose a new shape, choose a new colour and save the image. While drawing these 4 actions can be performed intertwined in any random order and in any random quantity, only guided by the whims of the user. There is also the choice of creating a new image from scratch or editing an existing image to create a new image.

Answer 1

Very simple solution to you question is below.

Please do not omit the guards after decision node if you don't want to have an undeterministic behaviour of your activity. Decision node offers a token to the first flow that have true guard whereas the order of evaluating of the guards is not defined.