This is SP2010 / NW 2010. I've got a library with a small handful of Nintex Workflow workflows bound to it. Until recently, I could access those workflows while browsing the libarary, by navigating to Library Tools > Library > Workflows > Workflow Settings. However, I no longer see any Nintex Workflow options in that Workflow Settings menu. I can, however, access the worflows at the Site Collection level by visiting Site Actions > Site Settings > Nintex Workflow Gallery.
I'm not sure why those Nintex workflow options disappeared from the Workflow Settings menu.
Solved! Go to Solution.
Make sure that the Nintex Features are still activated for that site. Go to site settings > Manage Site Features and then look for the Nintex features to make sure they are active. You can also look under the Site Collection features section to make sure everything is still active there too.
If you had the problem I did this is an absolute simple solution. Try widening the width of your browser. If it isn't wide enough, you can't see the option but it is there. I've made this mistake twice!!
After navigating Library Tools->Library, you don't see the icon on the far right with the check mark in the circle. For me, that is the 'Workflow Settings' icon. I don't have a 'Workflows' option.
Please review my article regarding missing Nintex icons in the ribbon:
This should help with the issue you are experiencing.