Not sure why you have Z_Max as your Probe Pin since the Z Probe for a delta should be on the Min Endstop.
But to disable/enable software endstops, in configuration.h set these lines as shown:
#if ENABLED(MIN_SOFTWARE_ENDSTOPS) || ENABLED(MAX_SOFTWARE_ENDSTOPS)
#define SOFT_ENDSTOPS_MENU_ITEM // Enable/Disable software endstops from the LCD: You'll need this enabled when setting Z-Probe Offsets
#endif
This will put a menu item under Prepare -> Move Axis (after doing Prepare -> Auto Home) called 'Software Endstops' that will allow you to enable/disable them.
Then you can (carefully) move the z axis below zero to adjust bed height.
Hope this helps.