I just started to use and customize gmb and am amazed of how flexible it is *wow*  :o

However, while customizing I tried to include some sort of quick labeling of the current song. If I'm right there is the AddLabelEntry widget and I can use %L to display the current song labels. What I'm missing is the ability to quickly add/remove tags. The AddLabelEntry is already fine for adding labels, but to remove them I have to use the song properties dialog. My suggestion is to add a cloud-like widget (all labels a equal-sized) that lists all current labels. If you click on a label, it gets removed. New labels would be entered by the AddLabelEntry as it's already implemented.

The v1.1.x branch has the LabelToggleButtons widget that does that (with a checkbox next to each label)
I really need to document the changes in v1.1.x

Ah, forgot to mention it. I've already looked trough the code and tried out the LabelToggleButtons, but I found it too heavy for what I wanted to archive. If you place this widget so that it does not take up much space (I use a whole lot of labels) there's too much scrolling needed to set some labels.

PS: I'm on "latest" (shimmer) version