Here is a simple Screen Flow that lets user quickly create an Opportunity and a Quote with one click. Customer wants to keep just a single screen and prefers Flow over LWC (for maintenance concerns). The task is: when user selects Account (1.) then dynamically fill in Opportunity Currency (2.) field with the Account Currency.

I used Data Fetcher to obtain Account's Currency - and this part works fine when an Account Id is hard-coded. But I can't pass selected Account Id to the formula. I get an error "The "basicAccountId" resource can't be used as a merge field."

What else I tried - Manually assign Output Value to a Variable - it doesn't work dynamically

Any idea on how to bypass this Salesforce limitation?

Here is a simple Screen Flow that lets user quickly create an Opportunity and a Quote with one click. Customer wants to keep just a single screen and prefers Flow over LWC (for maintenance concerns). The task is: when user selects Account (1.) then dynamically fill in Opportunity Currency (2.) field with the Account Currency.

I used Data Fetcher to obtain Account's Currency - and this part works fine when an Account Id is hard-coded. But I can't pass selected Account Id to the formula. I get an error "The "basicAccountId" resource can't be used as a merge field."

What else I tried - Manually assign Output Value to a Variable - it doesn't work dynamically

Any idea on how to bypass this Salesforce limitation?

EDIT: Extra screenshots of how I wanted to use the merge field with Data Fetcher, no success: