To add tags, you just add tag(s) to a task.

To add locations, go to the tab Locations and add the location there. Some people use tags for locations too.

Thank you for your reply, but the problem is: How do I create at new tag to add to a task.
Normally I would have to do that in the Settings/Tags pane, but I have no longer a "+ add tag" there. It's gone.
The button is available for adding lists, but not for adding tags or locations.

You don't need to create tags in advance, just add them to the task in question and it's created. The tag tab is for merging or deleting tags you don't want any more. I have a strong feeling that there never was a "+Add tag" in this tab.

Locations are created at the Locations tab.

Thanks Rajjan
That did the trick. Now I get it.
It might be a good idea to introduce this feature though.
I will give an opportunity to manage tags (and locations) in the coherently to how lists are managed. You could still keep the already established methode running. Many roads leads to Rome.