yes. This can be added mid-game.

If you continue to see the variable names instead of the mission text, please let me know. There is a vanilla bug where the mission is a bit slow to load and update the text but it should not persist. This usually means there is some sort of error. Please let me know if you see any console errors. You can open the console with '

Also is this able to be added mid game? Cause you make some dam good Mission mods, and I low your weapon mods...well I dont use all the weapon mods, but yeah they are fun.

When accepting the mission it shows the variables instead of the quest received from.

This is what is displayed when you look at the mission details in the missions pane.
You received the following request from the ${sectorName} ${giverTitle}

...

- ${killedTargets} / ${targets} targets killed

I do have your extra mission mod installed, not sure if there is a compatibility issue.
This is the "only" other mission mod I have installed.