change document workflow state from an other workflow

As a general point I would avoid having separate workflows here.

Whilst it is possible to set the workflow and workflow state properties via script, M-Files will also try to validate that the move is "valid" (i.e. there's a valid transition from X to Y), which there never can be between workflows, so typically fails.  What's worse is that it may look like it's working during testing (as admins can do anything, and we often test as admins), but it fails as a normal user.

It's possible to get around this by tricking the system using automatic state transitions and things, but I stand by my point: I would avoid having separate workflows if at all possible.

Hi Craig

What to do in this case, because a proof of payment may be linked to several invoices or be used more than once, which is not good.

Hi Craig

What to do in this case, because a proof of payment may be linked to several invoices or be used more than once, which is not good.

Difficult to say without seeing the vault structure.  It's possibly best to reach out to your partner for some support.  They can spend some time looking at what you have and what you want to achieve, and guide you on the best course of action.  That's quite difficult via a forum.