We have a dimension that won't unload completely (keeps 1 chunk loaded) and as such can't use safedel.

Unfortunately rftdim help doesnt list the deldim subcommand, and using rftdim deldim anyway results in: Unknown RfTools command: deldim.

Has this been removed by accident?
Version 1.12-7.23

Looks like it was removed as part of 2fad404 and just never put back. Note that in the future, bugs affecting RFTools Dimensions should be filed under McJty/RFToolsDimensions rather than here.