I confirm that [Save BMP] and [Copy BMP] in DGIndexNV properly honor the display area and cropping.

Your fixed version work like a charm for me.
Tested on a sample coded 1088 with display area 1080:
- Cropping only -> OK
- Resize only-> OK
- Cropping with Resize -> OK

Thank you I'll test it tomorrow but before I've a question: is it problematic to use your dgdecode 64bit version with a 32bit version of avisynth+ ?

If your solution could satisfy most users, your choice make sense.

Did you mean to remove "Always Crop 1088 -> 1080"? Edit, it still seems to crop to 1080 That option never made any sense so you can pretend that it is always on. There's no reason not to always honor the stream's coded display area. I agree 1088 is autocrop to 1080 but once you set a crop value it ...