Cura-MeshTools VS mks-wifi-plugin

Yes, it could be MeshTools. My bad. See these instructions: https://github.com/fieldOfView/Cura-MeshTools/issues/36

If you want the thumbnail out of Orca I'd think you could take that code and port it to whatever and add it is a post processing script. You'd just need to find the base64 PNG in the gcode, decode it, and run it through your process to generate the funky thumbnail. There's some Python in here that does similar RGB bit shifting but I didn't look close enough to see where/if they differ: https://github.com/Jeredian/mks-wifi-plugin/blob/develop/MKSPreview.py .

No that's different than what I'm talking about, what you are referring to is a hardware upgrade, I'm referring to the software plugin for Cura that generates a compatible thumbnail for the mks tft screen, that same plugin will also allow you to connect cura to the hardware addon but even without that you need it installed.in cura if you want thumbnails. https://github.com/Jeredian/mks-wifi-plugin just above the install instructions is the relevant bit: "Get preview on 3D printer srceen when using MKS Robin TFT35 or MKS TFT35 LCD."

See https://github.com/Jeredian/mks-wifi-plugin/issues/171

Regular Cura doesn't add bitmaps to the gcode file. The option may be greyed out because the MKS plugin doesn't support a bitmap for your printer. You might be able to contact the developer of the plugin on Github and ask a question there.