As wjervis mentioned, Microsoft rolled out a feature in Office365 to limit the amount of scripting allowed in order to maintain the security and integrity of the sites in a tenancy.
When the cutom scripting is disabled, parts or features that support scripting are no longer visible.
Here is how to check:
- Log into Office 365
- Click the Office 365 header link in the top left.
- Click the Admin Panel from dashboard
- In the left menu, scroll down to Admin section and click to expand
- Then click SharePoint.
- In the SharePoint admin center. In the left menu, click settings
- Scroll down and find the Custom Script section.
There are settings to Allow or Prevent scripting from running of personal or self-service created sites. If they are set to Prevent you may not see the settings you mentioned.
You will have to determine if you want these turned on.
For more information, see http://go.microsoft.com/fwlink/?LinkId=397546
You can achieve this with power-shell commands as well.
Step 01: Open the SharePoint Management shell
Step 02: Type the below command to connect with SharePoint Admin Center in management shell. You have to replace your admin center url which is in line 1.
$spadminurl = "https://tanent-admin.sharepoint.com/"
connect-sposervice -url $spadminurl
Step 03: You will be asked to enter user name and password.
Step 04: Enter the below commands. You have to mention your site collection url where you need the sections.
$spsiteurl = "https://sitename.sharepoint.com"
Set-SPOsite $spsiteurl -DenyAddAndCustomizePages 0
For more information you can view the below blog post.