You want to configure a known customizing point however you don´t find the option in Manage Your Solution.
S/4 HANA CLOUD
You can find in the Roadmap viewer the Expert configuration and SSCUI file for every Cloud Release.
Here you can find the link to the file.
Please check if the configuration point exists in this file.
Check the Column 'Configuration Step Available in Configuration Your Solution'.
In case it says yes, you will find the configuration entry in Manage Your Solution.
In case it says No, you have to create an incident for a TESTER system with the component XX-S4C-SRV-CON.
In case the point is not included you can contact your product expert to follow the review process for non standard expert configurations.
S/4HANA CLOUD , KBA , MM-PUR-GF-PR , Price Determination , MM-FIO-PUR-REQ , Fiori UI for Purchase Requisitions , MM-FIO-PUR-PO , Fiori UI for Purchase Orders , Problem