Unlock Android 15 System Write

My Android 15 tablet is already rooted with Magisk, yet /system stubbornly stays read-only. I’ve tried handling it through Root Explorer, but every attempt throws a “permission denied” message and nothing ever sticks.

I’m looking for a reliable, repeatable way to remount /system as read-write and keep it that way after each reboot. Whether the solution involves ADB commands, a patched boot.img, fastboot tweaks, dynamic-partition fixes, or another approach, I just need it to work without breaking Magisk or failing basic integrity checks.

Deliverable
• A concise, step-by-step procedure (or ready-to-flash/execute files or script) that lets me write to /system and confirms success in Root Explorer—no “permission denied”.

I have a tab with root access ready and can test changes live while we chat, so we can close this quickly once write access is verified.