I asked for the same feature several years ago (delete from an SMB share that gives the logged-in user those priveleges) and unfortunately, SKYBOX VR still has not provided this feature. However, I found a workaround that works perfectly well and allows me to delete a file from an SMB share within SKYBOX.
I'll explain my workaround, but it might not work for you because I see you are using the Quest version. Perhaps it would work if you can link to a PC with the link (USB) cable?
I have a Rift S, which is connected/wired to a PC. On the PC, I can map an SMB share to a local drive letter. In my case, I have mapped the SMB share from my Drobo NAS to local drive letter P: on my PC.
Then, within SKYBOX VR, rather than use the "Network" tab to connect to that SMB share, I access it as if it were a local drive, as the P: drive.
Accessing it that way, SKYBOX VR thinks it is a local drive, and allows me to delete files using the wrench icon.