I am having the same issue. The workaround I used was to export to json, edit the json file, and then uploaded the file via the workspace New menu item.
Steps:
1. From Power BI, view the workspace with the dataflow
2. Click the More Options icon on the row (the three vertical dots adjacent to the referesh icons)
3. From the context menu (see image in egbertdejong post above), select "Export .json"
4. Edit the json file - luckily the name and description elements are the first things:
{"name":"some flow name you want to change", "description":"some description you might want to change", ...}
Be sure that the file is saved with the .json extension.
5. From the Workspace, click "+ New v" and select "Upload a file"
6. From the "Discover content" page, select Local File or other appropriate choice.
7. Select the file and load it.