Provide ability to add a sub tag to an existing tag

In the current version I can only add a new tag using the three dots menu in the TAGS sidebar item.
Adding a new sub tag to an existing tag difficult because I need to enter the full text of the existing tag hierarchy to the 'Create a new tag' dialog box before entering the new sub tag. I can copy and paste the existing tag text, but it is rather inconvenient. It would be great if you could add a 'Create new sub tag' menu item to the tag menu for every tag. This would make it mush easier to build out a deeper tag structure.