I can't see any problem in a virtual interview (the interviewer won't probably even notice).
In a real one, it could look a bit strange to the interviewer but if it is useful for you I don't think there could be issues.
In terms of how to take notes, I would suggest to divide the first page into 4 parts as below:
- top-left: who is the client
- bottom left: initial information
- top right: objectives
- bottom right: structure
Landscape format in general works better. Sometimes you will have to go back and forth, as you may get information, objective 1, additional information, objective 2, etc.
The vertical line should be closer to the left border and the horizontal line should be closer to the top border so that there is more space for the structure.
After the first page, you can structure as below:
- top-left: name of the first area analysed
- bottom left: structure for the first area
- top right: name of the second area analysed
- bottom right: structure for the second area
The vertical line can now be in the middle so that the left and right parts have the same distance.
Besides that, you can also improve your notes with the following:
- Ask the interviewer to repeat in case you missed information. It is better to ask for missing information upfront rather than later
- Do a recap after the prompt. This ensures you took notes correctly since the interviewer will correct you otherwise
- Use abbreviations. Eg, for revenues use R, for costs use C, for increase use an arrow directed up, etc.
- Write down essential information only. You do not have time to write everything, thus you should exercise in writing down only the necessary information. If you have a client that produces steel which has four plants, with a revenue problem, your notes could be something as Steel producer, R (arrow down), 4 plants
- Keep a separate sheet for math if you tend to be disorganized in that part
Hope this helps,