How to create dynamic parameters in confluence macros body?

I am developing confluence plugin using Atlassian SDK.The thing i want to do is dropdown list with dynamic values and dynamic number of values. This dropdown list should be in confluence macro body.There is some API on internet where i get these values from.Now i am hard coding these values in atlassian-plugin.xml file. Tag

<xhtml-macro><parameters><parameter><value>. . .</value></parameter></parameters></xhtml-macro>

The options I've tried :

• Velocity template
• All types of xhtml-macro, category
• Rest request to my backend app (Stuck with next exception - The origin server did not find a current representation for the target resource or is not willing to disclose that one exists)
• I even tried to create atlassian-plugin.xml and export it to target/classes folder

Can someone tell me the right solution to achieve my goal please?

Screenshot

atlas-versionATLAS Version:    8.2.7ATLAS Home:       /opt/homebrew/Cellar/atlassian-plugin-sdk/8.2.7/libexecATLAS Scripts:    /opt/homebrew/Cellar/atlassian-plugin-sdk/8.2.7/libexec/binATLAS Maven Home: /opt/homebrew/Cellar/atlassian-plugin-sdk/8.2.7/libexec/apache-maven-3.5.4AMPS Version:     8.1.2