for the "readonly" you can use the "HTML attributes" behavior and add:
readonly=readonly
for the Community Builder fields you need to read the values of the current logged in user from the community builder database table using a Read Data action, you can ask the CB team how to read the values from the database
or if CB sets these values in the user's session then you can get them using: {user:cb_iban}
Max, ChronoForms developer
ChronoMyAdmin: Database administration within Joomla, no phpMyAdmin needed.
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if CB has the values in the session then just using {user:cb_iban} will be enough, did you try that ?
if not then the Read Data config depends on how CB stores the data, I do not know how CB stores the data, but they will know, so based on their instructions you can configure the Read Data
you may also check the database tables yourself, find which table has the user data and let me know, and if possible post a screenshot
Max, ChronoForms developer
ChronoMyAdmin: Database administration within Joomla, no phpMyAdmin needed.
ChronoMails simplifies Joomla email: newsletters, logging, and custom templates.