CMS Made Simple Forums

If you install a fresh version of v2.2.3.1 without the demo data (untick the option during installation), it is not possible to add a new stylesheet in the design manager.
The button "create a new stylesheet" is not displayed as you just receive an empty list

I was unable to verify this, it works fine for me. Perhaps try a browser cache clear, and a cmsms cache clear?

If that doesn't do it, check the error console and error log for any culprits.

If you still have the problem, you'll need to provide exact steps and server environment to recreate.

I guess the issue was the Apache module "ModSecurity". If that one is enabled, it messes with the display of the stylesheets in the Design Manager.

According to the CMSMS documentation, the ModSecurity module is not supported - is there any way to circumvent this issue?

Ask your hosting provider to disable it for your install.

If the host won't remove it, and switching hosts isn't an option, they should be able to check their logs and see which rule is causing the problem and whitelist it. You'll most likely run into more though, so be prepared to contact them regularly.