Is there a way to configure a container field to go directly to signature entry upon tap?
Check out this post.Restrict container field to signature only?
The answer is from philmodjunk
Just as philmodjunk suggested, use the 'Insert from Device...' script step, which allows you to choose 'Signature' as an option.
You could make the container field itself a button that just has a 'Single Step' action of 'Insert from Device...', or have it 'Perform Script' which allows you to add in all sorts of other steps and logic depending on what you need. The script could be something like as follows, which checks for if there is already a signature on the field, as well as checking if the user taps 'Cancel' instead of 'Accept' when entering the signature:
Retrieving data ...