Hello, I just upgraded to 3.0 yesterday and found that under legend, selecting 'New Column' for a layer does nothing in the Legend. Went back to 2.9.x on another PC and it seemed to be working fine and creates a new column. This is really annoying. Has anyone else noticed this? Thanks.
Sorry you're running into this. I'm unaware of any known issue with version 3.0 where "New Column" is not working. I did a very quick manual test and was unable to reproduce the issue you describe.
It is likely that the issue you are seeing is particular to the legend settings you have (such as the fitting strategy) and quite possibly the layer structure (such as the inclusion and make up of group layers). It is important to know these particulars in order to reproduce and fix the issue.
Can you contact Esri Support? They are better equipped to handle troubleshooting steps and gather bug data. They can be contacted at https://support.esri.com/en/contact-tech-support.
Thanks for the feedback!