Magisk doesn't modify the /system partition directly. It overlays changes, meaning you can often revert the "change" simply by disabling a module.
Changing IMEI with Magisk: The Exclusive Guide to Root-Based Spoofing change imei with magisk exclusive
Most modern IMEI changers for Magisk require the (the successor to Xposed). Download the LSPosed (Zygisk) module. Install it via Magisk and reboot. Open the LSPosed manager from your app drawer. Step 2: Use an IMEI Changer Module Magisk doesn't modify the /system partition directly
Note: This specific command varies significantly by manufacturer (Samsung vs. Xiaomi vs. OnePlus). change imei with magisk exclusive