Here is AMD instructions on how to change from Graphics to Computer mode: https://www.amd.com/en/support/kb/faq/dh2-024
But if in Radeon settings doesn't have the option to change from Graphics to computer mode probably indicates that your GPU or laptop doesn't support that feature.
The GPU Workload Compute/Graphics mode is not compatible with all AMD GPU Cards.
I would open an AMD Service Request (Official AMD SUPPORT) and ask them if your APU and GPU in your laptop supports Compute/Graphics mode or not: https://www.amd.com/en/support/contact-email-form
But from what I know, if a feature in Radeon Settings is not showing is generally indicates that it isn't supported by your GPU or APU.