min char is set at the time of HTML generation. I am not sure if it can be replaced after getting a value from the user. Inspecting the autoComplete shows that it is part of the HTML generated -- data-attributes

<input data-test-id="20200521095032084011165" type="text" data-ctl="[&quot;AutoCompleteAG&quot;]" autocomplete="off" autocorrect="off" autocapitalize="off" role="combobox" name="$PDeclare_UIGalleryControls$ppyAutoCompleteProperty1" id="pyAutoCompleteProperty1" data-skip-ac="yes" class="autocomplete_input ac_" value="" data-attributes="[ &quot;EXPANDEDSubSectionpxNewAutoComplete11_pyAutoCompleteProperty1&quot;,2,0,{},&quot;Declare_UIGalleryControls&quot;,0,false]" data-changed="false" data-old-value="" data-back-nav-id="key1">

you can try to modify this by using JavaScript -- not sure if it'll take effect. I tried to , but did not see desired results. When I tried from developer toolbar , it did seem to take effect.

You may want to check if saving the current control -- and modifying it suit ur needs help. But you do run into maintenance and other issues.

Any suggestions ?

I can't seem to think of a straightforward way to do this. Lets wait for other experts to weigh in.