This conversion represents the standard workflow in CADKEY software, where you can use .ckt templates to quickly create .ckd designs based on predefined settings. It does not seem possible to repeat this in another tool, so the original tool remains the only choice.
Convert CADKEY template file to CADKEY design.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert ckt to ckd on Windows
A program used for modeling CAD 3D wireframes
Convert from ckt file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.