Adding a new translation key will allow you to do a few things, (1) you can add text that shows up on your marketplace, which can be can be translated to a different language if needed, and (2) you can also add a hint or placeholders to various items on the listing form.
To add a new key go to Settings > Languages. Click on "Add Key" in the top right corner.
Once you are on the Add Key page, you can input a name that can be referenced in liquid and also add the default text and then hit save. You will then be able to change the default text and translate to multiple languages if needed.
To add a hint to your forms for RFQ, use the format 'simple_form.hints.transactable.action_rfq' for the *Key and Choose the text to be applied to your hint in the *Default English text field and click save.
In this scenario the default hint text will show up on the front end listing form if that item is turned on for your listing form.
**Keep in mind - This may not work for all attributes, as some attributes are output using custom code that may neglect to output the hints.