I cannot seem to edit my variations on existing listing

Hello

I sell personalised prints in the handmade section. I have several existing listings that have variations basically a choice of frames.

I have just gone to remove one of the frame choices and I cant seem to do it.

I have gone to the inventory and then clicked edit on the relevant listing

I then went to variations expecting to see the choice of frames and it just says

“Variations are not available for this category”

How can I remove a frame choice from the “customise now” section?

Can anyone advise please

Thanks Paul