Connecting fields to a question in a form is great but in some cases not all options of a single-select or multi-select field need to be visible in the form, for various reasons.
For example, you have a custom field called ‘Channels’ listing ALL the channels that the Marketing team uses. However, you may want to create a form with a question that only lists some of those channels as options - not all options. But at the same time, you want to connect the question to the Channels field so it populates the value, which is then uses to trigger other rules when multi-homed into other projects, or quantified in Dashboards etc.
Just like the branch icon in the form, I would love to also see an 
icon to set an option to hidden, so it will not be visible in the form.
The current workaround is to create a separate copy of the single-select or multi-select field, but with the limited options (which will be connected to the question, in order to appear in the form) and then create a bunch of rule conditions to ‘sync’ this value with the value of the other field (that lists all options), resulting in two versions of the field within the same project.
This is clearly not ideal, not just from the visual issue of having two fields, but also resulting in maintaining two fields and their rules to keep them ‘synced’.