I have done that, as you suggest, and am presently waiting for a suitable opportunity to try manual targeting again in vanilla + Webster's GFO, just to check it is working. Probably I will go back to school and see what happens in there..
I thought I would be able to go to an attack screen and see dials which I could then toggle to be assisted or manual from within the game, but I do not see this - perhaps I am getting confused ( it happens!).
Went back to school. Manual targeting enabled and working in there.. (I missed).
Manual targeting is not working in game proper
No red marker available to put in the info for range, no stadimeter lines.. I made sure I had set it manual in options in the menu and at the start of the campaign and if I go back into options it is still set to manual, but it is not happening in-game.. back to reinstall and vanilla I guess.
Reinstalled, no mods on at all, manual targeting is now present in the game - hooray! I will add mods later, carefully and one-at-a-time!!