Bob, you’ve not seen it because it’s not been added yet. AxCrypt don’t have the resources to implement exotic features as a matter of priority. The main development effort is primarily in making the software stable, fixing any bugs and adding features requested by the majority. Hardly anybody wants command line integration so it’s very low on their priority list (judging by other posts on this forum).
If you were to make a large one-off donation (to fully cover the cost of developing/testing the feature) then they may be able to prioritise development of that feature, naturally you’d want to ask them first before committing funds.
The software is open source and you are welcome to add the feature yourself if you need it, otherwise I’m afraid there’s no definite date on implementation.