OK, maybe there are more like me that do not have any UVESA_MODE or S3 references in their menu.lst. First, do "VBoxManage setextradata "VM_NAME_HERE" "CustomVideoMode1" "320x480x32"" procedure through terminal. My custom videomode was "1920x1089x32"... (sorry, I use Linux, so procedure works on linux) for Windows, just add .exe to VBoxManage..
Look in the first entry as described before, this is the menu entry you would normally boot. I normally use nano as it works more easy for me. And nano happens to be present in Android >6 too. (other version not tried)
Procedure:
- Boot VM, chose the "debug mode" option to boot. Pressing "enter" after a while will result in the prompt
- Change directory to /mnt/grub "cd /mnt/grub"
- list directory content with "ls" (not necessary but I like to see where I am)
- copy menu.lst (make this standard procedure before changing anything) "cp menu.lst menu.lst.bak" (or whatever extension you like to use for backup)
- open menu.lst, e.g.: "nano menu.lst".
- look in first menu entry (normally there are 4, starting with the titles you see in the boot menu) the "kernel" entry, which ends with the word "quiet"
- replace "quiet" with something like "vga=ask" if you would like to be asked every time at boot for the screen resolution, or "vga=(HEX value)" as seen in surlac's anwer.
- exit and save, don't forget to actually save it! double check this. (ctrl+X, YES, Enter for nano)
- reboot VM with "YOUR HOST KEY" + "R" (normally "right control" + "R")
Hope this helps anyone as it did solve my problem.
edit: I see that I did place this article in the wrong place, since the original question is about another Android version. Does anyone know how to move it to an appropriate location?