Adding fields to Flag Lists I'm using the Flag Lists module to manage user wish lists. I need to add additional fields to the lists such as "body"
I go to /admin/structure/flags/manage/fl_template/fields add the required fields, save, rebuild flag lists, flush caches and attempt to edit existing flag lists or create new ones and I still only see the "title template."
When configuring flag(s) (using the Flag module), you can indeed attach fields to them. However when doing so, make sure to also be aware about (and do) what is described in Attaching fields to flags, i.e.:

By default, Flags use the &quot;JavaScript toggle&quot; link-type. While this allows entities to be flagged without reloading the page, users cannot set any field values with the Flag. In order for users to set a Flag's field values, you must use the &quot;Form&quot; link type.
Navigate to Administration &gt; Structure &gt; Flags page. Click the Edit link for the Flag. Scroll down to the Display Options box and select the Confirmation Form radio button.

If the above doesn't help (or if you've already configured your flag using a Confirmation Form), then you may want to look at Comment nr 1 in issue nr 2539868, which points to 2 more related issues.