Multiselect Picklist supported in Legacy Web Client?

Are Multiselect Picklists supported in Dynamics 9.1 On-Premise using the Legacy Web client?
You don’t have to use Unified Interface, do you?

I set up a field of type Multiselect Option Set, used an existing Option set with it, and added it to a legacy form.

On the form, there’s nowhere to edit or select the options. I am a System Administrator so I should be able to edit. What am I missing?