A couple of weeks ago we discovered a problem with free text invoice postings, that did not create a voucher after initial validation error, e.g. if you forgot to set some dimensions. We received a hotfix for this: KB4092585.

What this hotfix did though, was that: if you forget to set some dimensions on the line and header you first receive a message saying that account *** and account*** must have a cost center (for example).
* You can then go to the header > financial dimensions > add a cost center.
* BUT, if you shall add a missing dimension on the line, you NOW have to go into "distribute amount" > click correction > add dimension. You can not add dimensions for the line under line-details as you always have been able to do....

This is not how it has been working in previous version of Dynamics 365 (or previous AX-versions overall), and this is not a very user friendly solution.

We suggest that you bring it back to how it was before: that you can add any missing dimensions on the line on line-details > financial dimensions.