Hello, oh, checkbox list is a param array. The best way is to look into HTML code how fields look like. Important are parameters name and value of HTML form field.
For example checkbox list:
<input id="joomdoc_field1_0" class="checkbox" type="checkbox" value="1" name="joomdoc_field1[0]">
<label class="inline" for="joomdoc_field1_0">Tag A</label>
<input type="hidden" value="" name="joomdoc_field1[1]">
<input id="joomdoc_field1_1" class="checkbox" type="checkbox" value="2" name="joomdoc_field1[1]">
<label class="inline" for="joomdoc_field1_1">Tag B</label>
Pre-select Tag A
index.php?option=com_joomdoc&view=documents&joomdoc_field1[0]=1
Pre-select Tag B
index.php?option=com_joomdoc&view=documents&joomdoc_field1[1]=2
