Ender 3 pro prusa slicer issue

@Lenny M as for the M900... the printer is complaining that it doesn't even understand the M900 code at all... so my guess is that you need to remove the references to it in your PrusaSlicer config. Check the filament tabs custom gcode setting and remove it there. (That's where I see it on my printer.) As for the last part, I don't quite understand your question... you said "I changed T1-4 to T0"... where else are you talking about? (There is no need to change the Autogenerated Gcode if that's what you're asking, as we never insert a T commands... only comments.) As for Notepad++, you can use anything you want to edit... but I'd suggest that there might be a way to do it via a post processor... again, I've never run into this issue before... but I've seen where Octoprint complained about it, but it should be ignored by the firmware... I've actually never seen a printer complain about it. Is this a custom firmware? If so, maybe it's just a flag in Marlin to turn it off. A simple post processor that replaces those commands with T{#} to T0 or M900 to ;M900 will solve it.