Max length of 128 preventing saving lots of referenced entities

Problem/Motivation

When trying to save a node with many tags (using SHS), I get an error saying:

"{field name} cannot be longer than 128 characters but is currently {number} characters long."

When I inspect the HTML, I see that it saves the target IDs in a "textfield" form field, that has a maxlength="128" attribute. This is unnecessarily short and preventing me from saving the node.

When I review the module code, I see that in:
/shs/src/Plugin/Field/FieldWidget/OptionsShsWidget.php, in formElement(), line 164 is:
$element['#type'] = 'textfield';
which changes the field type to textfield. However that also uses the default maxlength of 128.

If I add the following line right after it:
$element['#maxlength'] = 500;
Then I'm able to save the node with way more tags.

But 500 is an arbitrary maximum length, so I'm not sure how to determine the ideal length.