Issue with using the skin

Hello,
I have an RB951Ui-2HnD router, and I have updated its RouterOS and RouterBOARD to the latest stable version, 7.23.2.

I am using webFig and the "Design Skin" menu, I apply my desired restrictions and save the skin under a custom name.
The save confirmation appears, and a file with that name is created in the "skins" folder within the "Files" menu.
However, when I return to the "Design Skin" menu, only the "default" option is available for selection or editing.
Similarly, in the "System > Users > Groups" menu, only "default" is available as a group skin option.
I read through previous forum discussions where it was suggested to edit the JSON file and replace double quotes (") with single quotes ('). I tried this and re-uploaded the file, but it had no effect.
I even saved the file in the simplest possible format containing just a single line of code (similar to the snippet I’ve provided below) but that didn't work either.

Can anyone help me with this?

Thank you in advance for your guidance.

Sample text from the file I created:

{
"Quick Set": 0
}