Of course....
The was my bad; I activated Scheduler (Options>Scheduler). I wanted to start downloading after midnight, so activated Scheduler not to download at that particular time, and then I had download speed (dark green) set up to max. By default that sets up the upload speed to 'unlimited'. I forgot about that and did not deactivate Scheduler. This caused all options on 'Connection' to be greyed out (not allowing me to set up the upload speed). When I deactivated Scheduler, the upload speed in 'Connection' was no longer greyed out; in fact reverted back to my original settings for upload.