There is a restriction on how many portlets users can add on Home Dashboard. User is limited by Add Content window available after clicking Personalize link.
If more portlets of a specific type is needed to be displayed than what is allowed in the Add Content section, create a custom center tab and add the portlets there:
1. Customization > Centers and Tabs > Center Tabs > New
2. Provide a Name (e.g. My Portlets) and Center where want to publish this tab in
3. Navigate to Content subtab > Portlets sublist
4. Add needed portlets in Type column and choose alignment in Column.
5. Ensure Show checkbox is marked for portlets.
Refer to topic Creating Center Tabs for more details.