Add text to MKV Export

Is it possible to add some text to an MKV file using the MKV export sample?

The Smart Client appears to have a Add Text functionality, is this possible with SDK? I have tried to activate the feature in the Management Client but it is always unavailable in the Smart Client even after changing the Smart Client Profile:

Smart Client does not support the use of video text when doing MKV export. (Only AVI export does.)

MKV export is optimal in that XProtect takes the raw unmodified camera data and exports, very fast and efficient. (No decoding and re-encoding.)

The MIP SDK is no different, MKV export is not modifying the data and thus no text can be added.