Hello Experts,
Obviously the workaround worked but only for a while. Now the theme exists in the list but I get:
com.sapportals.portal.design.PortalDesignException: DesignInfo "custom_theme" is not known by design manager. at com.sapportals.portal.design.impl.design.DesignManager.getDesign(DesignManager.java:165)
Any suggestions how to solve that now?