Did some testing with latest stable WinUAE, default A500 kick 1.3 Quickstart config.
All works as it should under kick 1.3, but in Kick 2.0 and 3.1 there is a bug. When you've pressed Esc to edit some code, then press Esc to go to the command line, the Asm-One screen is not updated correctly. Instead of putting the cursor at the bottom, below the status bar, it ends up at the top displaying ;1H after the commandline caret, and not clearing the screen (you still see code written all over the screen).
Tested at 1 fps to see if it types a character before the ;1H code which is then overwritten by the caret character, but it was impossible to see.
I've seen the bug in all Asm-One versions, and all it takes to fix it is to load kick 1.3. It works with kick 2.0+ on a real A500, A600, and A1200, of course, or I wouldn't report it
I'm using for example "Kickstart v2.04 rev 37.175 (1991)(Commodore)(A500+).rom".
Also tried with and without setting Full ECS+Chipset extra A500+ for this rom.
Tested with and without startup-sequence (ie. with and without relevant setpatch, if that could influence it).