Good point about button 0 but that, luckily, only applies if it is indeed a “button” and not a “switch”.
If button 0 is assigned as a “switch” its default behaviour does not work any more so you do not need special build with 5 buttons.
Unfortunately most of the controllers use flashing/programming button (usually GPIO0) as a primary input button (0) and, as mentioned above, that button (GPIO0) is not compatible with “switch” function. Still if the controller offers additional GPIO headers/exposed pins use those. In such case re-assign button 0 to some other GPIO.
You will loose On/Off button in such case but that is not needed in application as OP requested. In such case WLED must remain in On state at all times.