When you say 'edit mode' and 'display mode', could you explain what you are actually using? I noticed your other posts are often using the rich text editor which will escape any directly entered markdown tags so that they aren't rendered. On the other hand if you are in the markdown editor then you should be seeing them taking effect in both the editor and the viewer.
if you choose the split screen mode with the md editor in one half and the display showing immediately, then it will show as you wish and you avoid the inconvenience of not knowing whether you are in wysiwyg or not.
I've been looking at the option to see. The problem is that to me the split screen is never shown and it is strange.
I have the View mode (see note) or graphical edit mode but it never shows in markdown.
For example this is my setup and split screen or markdown mode is never visible:
In the top right of the screen is a little button between i and the bell (sorry im on mobile so can't annotate a nice pic for you). It will be active when you are on the viewer and will cycle between editor, viewer and split.
It should also be in the view menu on the top menu bar.
I am very grateful, as a simple button I have not been able to see it!
Now I do like how it works, thank you very much friends, you are all very kind !!