We introduce a human-in-the-loop one-shot voice conversion tool called CreakVC designed to modulate the level of creaky voice in the converted speech. Creaky voice, often used by speakers to convey sociolinguistic cues, presents challenges to speech processing due to its complex phonation characteristics. The primary goal of CreakVC is to enable in-depth research into how these cues are perceived, using systematic perceptual studies. CreakVC provides access to a diverse range of voice identities exhibiting creaky voice, while maintaining consistency in other parameters. We developed a spectrogram-frame level creak representation using CreaPy and finetuned FreeVC, a one-shot voice conversion tool, by conditioning the speaker embedding and the self-supervised audio representation with the creak representation. An integrated plotting feature allows users to visualize and manipulate portions of speech for precise adjustments of creaky phonation levels. Beyond research, CreakVC has potential applications in voice-interactive systems and multimedia production.