Opening a modal via checkbox in vue-bootstrap?

I see two approaches that I think are equally viable here:

1: Call modal instance method show(id) from checkbox handler

I think the simplest way to do this is to call the this.$bvModal.show(_id_) function to show your modal from the checkbox's change event:

<b-form-checkbox
  id="checkbox-1"
  v-model="healthDocument"
  name="checkbox-1"
  value="accepted"
  unchecked-value="not_accepted"
  @change="$bvModal.show('modal-1')"
>
  Health Documents
</b-form-checkbox>

<div>
  <b-modal 
    id="modal-1"
    title="BootstrapVue"
  >
    <p class="my-4">Hello from modal!</p>
  </b-modal>
</div>

This approach means that your modal's visibility isn't synced with the checkbox state, but that it will still open when you click the checkbox. If you want the modal to open only when the checkbox goes from unchecked to checked, then you'll need to add a conditional to the handler, so that it only fires when you're checking the checkbox:

checkHandler(checked) {
  if (checked == 'accepted')
    this.$bvModal.show('modal-1');
},

2: Bind modal state to checkbox state

I initially suggested to use the modal's v-model directive, but checkbox state is a little funky in that it doesn't necessarily store true/ false– it will actually store whatever value you give it as it's "checked" value. In your case, that's the string "accepted".

So instead of v-model, I suggest using the property that underpins Bootstrap-Vue's modal's v-model directive: visible.

This way, the modal will be in sync with the checkbox's checked state, so that when the checkbox is checked, the modal will be open, and when it's unchecked, the modal will be closed. This makes sense if you want the checkbox to control the modal directly.

This also means that to dismiss the modal, we'll need to programmatically uncheck the checkbox (which may or may not be desirable based on your use case). Here's the full code example:

<b-form-checkbox
  id="checkbox-1"
  v-model="healthDocument"
  name="checkbox-1"
  value="accepted"
  unchecked-value="not_accepted"
>
  Health Documents
</b-form-checkbox>

<div>
  <b-modal 
    id="modal-1"
    title="BootstrapVue"
    :visible="healthDocument == 'accepted'"
    @hide="healthDocument = 'not_accepted'"
  >
    <p class="my-4">Hello from modal!</p>
  </b-modal>
</div>