LabelImg is now part of the Label Studio community. The popular image annotation tool created by Tzutalin is no longer actively being developed, but you can check out Label Studio, the open source data labeling tool for images, text, hypertext, audio, video and time-series data.
For now is https://github.com/heartexlabs/labelImg/blob/b33f965b6d14c14f1e46b247f1bf346e03f2e950/labelImg.py#L702
the 'H' in link should be lowercase, otherwise it can't jump to the right paragraph.