entering tags/kv-pairs should be the same across variables/check tags

Checks have key value pairs added like so

Variables have the user input things of the form
```
a,b
c,d
```

Start by comparing the check tag key-value entry flow with the variables input described in the issue and shown in its screenshots. Identify the existing UI entry points for both behaviors, then make their key-value input format consistent and verify that both checks and variables accept the same form.

Written by the indexing model from the issue text.