pass multiple values to multiselect box from radio input

[alex_tc80]

Regarding the dasboard input panels
Im trying to set values into a multiselect when i select a certain radio option.
Basically i have 2 fields:
1) multiselect that can have values a and/or b
2) radio with 3 options, first set multiselect to value a, second to value b
and the third one SHOULD set it to a AND b.

I would expect when clicking the third option, the multiselect box
to show BOTH option A and B, but instead it just lists a single unknown option "a , b"
This is a screenshot may it explains better (3 clicks):

I tried multiple combinations with no success.

I've read https://docs.splunk.com/Documentation/Splunk/8.1.0/Viz/tokens#Define_tokens_for_multiselect_inputs   , didn't help 😞

I also tried with no success what was suggested in
https://community.splunk.com/t5/Dashboards-Visualizations/Multiselect-Tokens-not-passing-values/m-p/...

The problem is also related to the escaping of the data.(see old thread) 
When DOM inspecting the multiselect, i get 
data-test-values="["a","b"]"   when manually setting a +b directly in the form.

When setting the XML to use <set token>a , b</set> DOM is data-test-values="[&quot;a,b&quot;]"
When setting the xml to use <set token="tok_multi">a" , "b</set> DOM is 
data-test-values="[&quot;a\&quot; , \&quot;b&quot;]"  🙂 (notice the backslash .... )

My version is Splunk Enterprise v7.2.9.1
The test dashboard source is:

<form>
  <label>Check MultipleSelect</label>
  <fieldset submitButton="false">
    <input type="multiselect" token="tok_multi" searchWhenChanged="true">
      <label>Aquirers</label>
      <choice value="a">TEXT1</choice>
      <choice value="b">TEXT2</choice>
      <prefix/>
      <suffix/>
      <valuePrefix></valuePrefix>
      <valueSuffix></valueSuffix>
      <delimiter> , </delimiter>
    </input>
    <input type="radio" token="tok_radio">
      <label>RADIO</label>
      <choice value="SETA">SET A</choice>
      <choice value="SETB">SET B</choice>
      <choice value="SETAB">SET A + B</choice>
      <default>SETA</default>
      <change>
        <condition value="SETA">
          <set token="form.tok_multi">a</set>
          <set token="field1">$form.tok_multi$</set>
        </condition>
        <condition value="SETB">
          <set token="form.tok_multi">b</set>
          <set token="field1">$form.tok_multi$</set>
        </condition>
        <condition value="SETAB">
          <set token="form.tok_multi">a , b</set>
          <set token="field1">$form.tok_multi$</set>
        </condition>
      </change>
    </input>
    <input type="text" token="field1">
      <label>multi token value</label>
      <default>$tok_multi$</default>
    </input>
  </fieldset>
</form>

[alex_tc80 · Accepted solution]

Instead of doing <set token>a , b</set> i used 

        <condition value="SETAB">
          <set token="form.tok_multi">a</set>
          <eval token="form.tok_multi">mvappend("b", $form.tok_multi$)</eval>

and it worked ! 🎉

[ITWhisperer]

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