Better documentation / examples / utilities for working with query params and named form actions

Describe the problem

Using the default action persists current query params and sends them to the server.

The documentation for named form actions describes "adding a query parameter", however, the examples provided replace any query parameters currently present on the page with a new query string containing only the action name. To preserve the current query param and also add an action name, I've had to do the following:

<form action="{$page.url.search ?? ''}{$page.url.search ? '&' : '?'}/saveExposure" ...>

This probably won't work in the example where a form with a name action is submitted and then another form with a named action is submitted on the resulting page. In that case, two named actions will be present in the query string, since the named action is not removed on submission success.

A utility to add or replace the current named action in the current page's query params would be extremely useful.

Similarly, in the action handler, redirecting from a form submission and preserving the query params, minus the named action, requires something like this to get a clean query param string for use in building a redirect url:

export function removeNamedActionParam(params: URLSearchParams) {
  const returnedParams = new URLSearchParams(params);
  for (const param of params) {
    if (param[0].startsWith("/")) {
      returnedParams.delete(param[0]);
    }
  }
  return `?${returnedParams.toString()}`;
}

It would be great to have this (or something like this) provided in the sveltekit library.

Describe the proposed solution

Utilities for adding and removing named action params from query strings, or documentation on how to do so. The current documentation assumes that named actions and query parameters will never be used at the same time.

Alternatives considered

No response

Importance

would make my life easier

Additional Information

No response

Start with the linked named form actions documentation and review its examples alongside the reported query-parameter behavior. Done means documenting or providing utilities that preserve existing parameters while adding an action and remove named action parameters when building redirects.