Create folder: access denied

I've tried to install the gmic plugin on affinity photo 2.6.3, which worked quite well. However when I tried to start it i've got the attached note that I have no access to create this directory

<img width="301" alt="Image" src="https://github.com/user-attachments/assets/4fe077f4-0309-4048-bdae-c29532442e28" />

Thank you for your help!