Hi @data_data -
While you can’t enter a $lookup stage directly in the query bar, the Lookup Field option does the same thing (you can see what pipeline it generates on the […] menu at the top right). I can’t tell what you did wrong with the Lookup Field option without more detail, but possibly you selected the incorrect fields. Feel free to share more info.
If you do want to use $lookup directly, you can do this by putting the pipeline into a Charts View and building a chart from that.
Tom