As a new user to the Web version, I find the Current Tag UI/UX in Entity Info a little confusing. Specifically, the X doesn’t seem to do anything. I would expect it to remove the tag from the currently selected entity, however it seems to not do anything.
Actually, I think a better placement for the X would be on the main level so one could remove the associated tag without having to enter a sub menu. 
The x does not “de-tag” anything, it selects the active tag and should be always be left on untagged. To remove a tag from any item change it’s tag to “untagged”.
Hmm… I’m not sure I follow. I fully accept that I’m new to this UI, but if you hover over the x you’ll notice it says “Delete Tag”, but clicking it appears not to delete anything.
My point still stands, it seems to be non-functional here and a better placement would be up a level (or perhaps in both locations), IMHO.
You are correct. It took me a moment to find where you were in the interface on Free, and to investigate it a bit. The screen recording you show is from the pop up tags list accessed from within the Entity Info window. That list is only for choosing a new tag to be assigned to the currently selected entity. The intended work flow would be, select an object, click on the current tag assignment in the entity info window, choose a new tag from the list, done. To “un-tag” an object use that same pathway and assign the object “untagged” which is the default state of all newly created geometry.
You are correct that the X in that position has the tool tip of “Delete Tag” and that it does not do anything. That is not the correct location in the UI to delete or manage tags so I don’t know why the x is there, nor why it does nothing. I’ll ping @Mark with SketchUp to have a look.
To delete or manage tags one would use the Tags Panel, which has it’s own icon in on the right hand side menu. From this panel you can add new tags, rename tags, change their properties like color by tag or edge type and also delete tags via the three bullet icon on to the right of each tag in the list. This is also the place to change the visibility of state of each tag, to hide and show objects using the eye.
Yup, I agree: this ‘X’ should not be there. I’ll get this clean-up issue on the team’s radar.
Thanks! Just a suggestion, but I still think it would make sense moving it up a level to the Current Tag of Entity Info as a way to quickly untag.