Every diagonal, row and column should add up to the same number, but this number is unknown.
Since you gave us a complete diagonal, isn’t the number known? Or are you counting adding 4+5+6 as part of the puzzle?
I think the instructions would be more fitting and the puzzle more puzzling if fewer numbers were filled in. E.g.,
| ? | 7 | 6 |
| 9 | ? | ? |
| 4 | ? | 8 |
| ? | 7 | ? |
| ? | 5 | ? |
| 4 | ? | ? |
Though having a lot of unknowns could be tedious.
Not that it matters for solving, but are the only allowable numbers in magic squares 1-9 (squares can’t contain, say, 35)? That might be fair to mention.
In addition to *text_image, you can also have dark mode versions of images and use *if (choice_nightmode) to display the correct one, as described here: