CMX is legacy and read-only here
CMX is an older vector format. It can usually be opened and converted from, but it's long obsolete, so there's no modern encoder to create new CMX files.
Looking for PSD to CMX? Here's why CMX isn't an output option — and the modern formats to use.
We don't create CMX files — it's a legacy format that's effectively read-only. Here's what to convert to instead.
CMX is an older vector format. It can usually be opened and converted from, but it's long obsolete, so there's no modern encoder to create new CMX files.
For a file that opens everywhere, convert your PSD to PNG, JPG or TIFF instead.
PSD is Photoshop’s native format, preserving layers, masks and effects for non-destructive editing.
How to open PSD opens in Photoshop, Affinity Photo, GIMP and Photopea.
Full PSD format guide