The point of a static pi is that it is static i.e. you do not move it between networks and you have full control of the network. If you think you will be moving the Pi then DO NOT set the address up on the Pi but set it up on the local router or computer the issues IP addresses on the network (DHCP server such as pi-hole)
To stop the allocation of the address to another device you reserve addresses on the router using the MAC address of the device and make sure this is outside the DHCP address range managed by the router.
You can set multiple addresses within dhcpcd.conf by the use of the arping direct BUT this requires you know details of the networks you are going to connect to and in best case the actual MAC details of devices on the network and from your question I do not think you know what network you will be connecting to. Details of this can be seen here