Change PHP version in MAMP 5

High Sierra

MAMP 5.5

I want to change the version of PHP that MAMP is using, the method mentioned here, which I used previously doesn't work with MAMP 5: How to change PHP version on MAMP 4.1

I have removed the PHP version folders from the MAMP/bin/php folder, but still the only versions that appear in preferences are

7.2.21

7.3.8

even though these are not in the MAMP/bin/php folder

I have tried changing httpd.conf but my change gets overwritten when MAMP starts apache:

LoadModule php5_module        /Applications/MAMP/bin/php/php5.6.40/modules/libphp5.so
#LoadModule php7_module        /Applications/MAMP/bin/php/php7.3.8/modules/libphp7.so

How do I do this?