You can suspend the passive device and make your changes. The configs will synch once you make suspended device functional again. >request high-availability state suspend > request high-availability state functional. You can also disable HA by unchecking "Enable HA" on the Device tab >High Availability.
Of course you can disable synchronisation of the configs in an HA pair, in fact it's required to migrate one to Panorama: https://docs.paloaltonetworks.com/panorama/9-1/panorama-admin/manage-firewalls/transition-a-firewall...
From the CLI:
user@device(active)# set deviceconfig high-availability group configuration-synchronization enabled no
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