If you want to dynamically define and export variable names in Bash here is the TLDR;
# Define the name of the variable
# Declare it and export it
declare -gx "$key"="some-value"
To then access that value via a dynamically generated variable name
# Create a variable that contains the variable name
# Read the value
Read the man page for
declare for more details and read this article for a really good explanation and further examples.
To read the
declare man page