You'll need to use a loop to iterate through and check each variable in the set.

Also, you should only call Set Business Process Variables once. If you call it multiple times inside a loop, you'll only end up with the last value because each iteration will overwrite the previous, meaning you'll need one or more multivalue tokens to update everything in one call.

In your workflow,

• Create a multi-value token to store your checked items
  • If you need to track multiple tokens, add a separate multivalue token for each item you need to pass back to Forms
• Retrieve your Table (not the individual variables)
• Add a For Each Row activity and use the table as the source
• Add your conditional sequence inside the loop and set it based on the checkbox
  • Select, Token > For Each Row > Column_Is Set
  • You should see an option for the checkbox like Variable_Option_Is Set that will return a true/false value for if that box is checked
• If true, append item information to your multi-value token(s)
• Outside of your loop, use Set Business Process Variables and set the variables you want to update equal to your multivalue tokens.