<div class="row m-3">

      <div class="col-sm-3 col-md-3 col-lg-3">

        <select id="categories" class="select" multiple>

<option value="1">Weather</option>

<option value="2">Forestry</option>

<option value="3">Wildlife</option>

<option value="4">Traffic</option>

<option value="5">Tourism</option>

<option value="6">Safety</option>

        </select>

        <label for="categories" class="form-label select-label">WORKING Categories</label>

    </div>

</div>

​

<div class="row m-3">

<div class="col-sm-3 col-md-3 col-lg-3">

This sample does NOT work

<select id="notcategories" class="select" multiple>

<option value="1">Weather</option>

<option value="2">Forestry</option>

<option value="3">Wildlife</option>

<option value="4">Traffic</option>

<option value="5">Tourism</option>

<option value="6">Safety</option>

</select>

<label for="categories" class="form-label select-label">NOT WORKING Categories</label>

 </div>               

</div>

​

const multiSelect = document.querySelector('#categories');

 const multiSelectInstance = mdb.Select.getInstance(multiSelect);

multiSelectInstance.setValue(['1','3','5']); 

​

//THIS DOESNT WORK

const multiSelect1 = document.querySelector('#notcategories');

                const multiSelectInstance1 = mdb.Select.getInstance(multiSelect1);

                values = ['1','3','5'];

                multiSelectInstance1.setValue(values);