I have tried to configure it like this:
env[TMP] = /srv/52559f90-1d49-4c27-93a2-63f2a2abff5b/www/nextcloud/tmp
env[TMPDIR] = /srv/52559f90-1d49-4c27-93a2-63f2a2abff5b/www/nextcloud/tmp
env[TEMP] = /srv/52559f90-1d49-4c27-93a2-63f2a2abff5b/www/nextcloud/tmp
But it still uses USB Drive (sde1) to temporarily save files.