How to edit boot options during linux booting?

The following steps worked for me in a Virtualbox Ubuntu VM:

• During the boot up menu, select the kernel version you want to boot with: 

                        

                        

• Press 'e' to enable editing of this line:

                        

• Go to "linux" bootline & add the boot options. I am adding slub_debug option in my screen:

                        

                        

• Do these boot options get retained across reboot?

          No.